diff --git a/lib/class-wp-theme-json-gutenberg.php b/lib/class-wp-theme-json-gutenberg.php
index 8dde6c399ba3f..8963e11095700 100644
--- a/lib/class-wp-theme-json-gutenberg.php
+++ b/lib/class-wp-theme-json-gutenberg.php
@@ -1133,6 +1133,7 @@ public function get_stylesheet( $type = 'all' ) {
 	 * Merge new incoming data.
 	 *
 	 * @param WP_Theme_JSON $incoming Data to merge.
+	 * @param string        $origin origin of the incoming data (e.g: core, theme, or user).
 	 */
 	public function merge( $incoming, $origin ) {
 
diff --git a/packages/edit-site/src/components/editor/test/global-styles-renderer.js b/packages/edit-site/src/components/editor/test/global-styles-renderer.js
index 9d0f510c4be59..37798630dcd8e 100644
--- a/packages/edit-site/src/components/editor/test/global-styles-renderer.js
+++ b/packages/edit-site/src/components/editor/test/global-styles-renderer.js
@@ -214,10 +214,20 @@ describe( 'global styles renderer', () => {
 			const tree = {
 				settings: {
 					color: {
-						palette: [
-							{ name: 'White', slug: 'white', color: 'white' },
-							{ name: 'Black', slug: 'black', color: 'black' },
-						],
+						palette: {
+							user: [
+								{
+									name: 'White',
+									slug: 'white',
+									color: 'white',
+								},
+								{
+									name: 'Black',
+									slug: 'black',
+									color: 'black',
+								},
+							],
+						},
 					},
 					custom: {
 						'font-primary': 'value',
@@ -229,18 +239,20 @@ describe( 'global styles renderer', () => {
 					blocks: {
 						'core/heading': {
 							typography: {
-								fontSizes: [
-									{
-										name: 'small',
-										slug: 'small',
-										size: '12px',
-									},
-									{
-										name: 'medium',
-										slug: 'medium',
-										size: '23px',
-									},
-								],
+								fontSizes: {
+									theme: [
+										{
+											name: 'small',
+											slug: 'small',
+											size: '12px',
+										},
+										{
+											name: 'medium',
+											slug: 'medium',
+											size: '23px',
+										},
+									],
+								},
 							},
 						},
 					},
@@ -264,10 +276,20 @@ describe( 'global styles renderer', () => {
 			const tree = {
 				settings: {
 					color: {
-						palette: [
-							{ name: 'White', slug: 'white', color: 'white' },
-							{ name: 'Black', slug: 'black', color: 'black' },
-						],
+						palette: {
+							core: [
+								{
+									name: 'White',
+									slug: 'white',
+									color: 'white',
+								},
+								{
+									name: 'Black',
+									slug: 'black',
+									color: 'black',
+								},
+							],
+						},
 					},
 				},
 				styles: {
diff --git a/phpunit/class-wp-theme-json-schema-v0-test.php b/phpunit/class-wp-theme-json-schema-v0-test.php
index aad503dc7c161..d2fd23e04edf4 100644
--- a/phpunit/class-wp-theme-json-schema-v0-test.php
+++ b/phpunit/class-wp-theme-json-schema-v0-test.php
@@ -335,129 +335,132 @@ function test_get_settings() {
 	function test_get_stylesheet() {
 		$root_name       = WP_Theme_JSON_Schema_V0::ROOT_BLOCK_NAME;
 		$all_blocks_name = WP_Theme_JSON_Schema_V0::ALL_BLOCKS_NAME;
-
-		$theme_json = new WP_Theme_JSON_Gutenberg(
-			array(
-				'settings' => array(
-					$all_blocks_name => array(
-						'color'      => array(
-							'text'    => 'value',
-							'palette' => array(
-								array(
-									'slug'  => 'white',
-									'color' => 'white',
-								),
-								array(
-									'slug'  => 'black',
-									'color' => 'black',
+		$theme_json      = new WP_Theme_JSON_Gutenberg( array() );
+		$theme_json->merge(
+			new WP_Theme_JSON_Gutenberg(
+				array(
+					'settings' => array(
+						$all_blocks_name => array(
+							'color'      => array(
+								'text'    => 'value',
+								'palette' => array(
+									array(
+										'slug'  => 'white',
+										'color' => 'white',
+									),
+									array(
+										'slug'  => 'black',
+										'color' => 'black',
+									),
 								),
 							),
-						),
-						'typography' => array(
-							'fontFamilies' => array(
-								array(
-									'slug'       => 'small',
-									'fontFamily' => '14px',
+							'typography' => array(
+								'fontFamilies' => array(
+									array(
+										'slug'       => 'small',
+										'fontFamily' => '14px',
+									),
+									array(
+										'slug'       => 'big',
+										'fontFamily' => '41px',
+									),
 								),
-								array(
-									'slug'       => 'big',
-									'fontFamily' => '41px',
+							),
+							'misc'       => 'value',
+						),
+						$root_name       => array(
+							'color' => array(
+								'palette' => array(
+									array(
+										'slug'  => 'grey',
+										'color' => 'grey',
+									),
 								),
 							),
 						),
-						'misc'       => 'value',
-					),
-					$root_name       => array(
-						'color' => array(
-							'palette' => array(
-								array(
-									'slug'  => 'grey',
-									'color' => 'grey',
+						'core/group'     => array(
+							'custom' => array(
+								'base-font'   => 16,
+								'line-height' => array(
+									'small'  => 1.2,
+									'medium' => 1.4,
+									'large'  => 1.8,
 								),
 							),
 						),
 					),
-					'core/group'     => array(
-						'custom' => array(
-							'base-font'   => 16,
-							'line-height' => array(
-								'small'  => 1.2,
-								'medium' => 1.4,
-								'large'  => 1.8,
+					'styles'   => array(
+						$root_name            => array(
+							'color' => array(
+								'link' => '#111',
+								'text' => 'var:preset|color|grey',
 							),
+							'misc'  => 'value',
 						),
-					),
-				),
-				'styles'   => array(
-					$root_name            => array(
-						'color' => array(
-							'link' => '#111',
-							'text' => 'var:preset|color|grey',
-						),
-						'misc'  => 'value',
-					),
-					'core/group'          => array(
-						'color'   => array(
-							'link' => '#333',
-						),
-						'spacing' => array(
-							'padding' => array(
-								'top'    => '12px',
-								'bottom' => '24px',
+						'core/group'          => array(
+							'color'   => array(
+								'link' => '#333',
+							),
+							'spacing' => array(
+								'padding' => array(
+									'top'    => '12px',
+									'bottom' => '24px',
+								),
 							),
 						),
-					),
-					'core/heading/h1'     => array(
-						'color'      => array(
-							'link' => '#111',
-						),
-						'typography' => array(
-							'fontSize' => '1em',
-						),
-					),
-					'core/heading/h2'     => array(
-						'color'      => array(
-							'link' => '#222',
-						),
-						'typography' => array(
-							'fontSize' => '2em',
-						),
-					),
-					'core/post-title/h2'  => array(
-						'color'      => array(
-							'link' => '#222',
-						),
-						'typography' => array(
-							'fontSize' => '2em',
-						),
-					),
-					'core/post-title/h5'  => array(
-						'color'      => array(
-							'link' => '#555',
+						'core/heading/h1'     => array(
+							'color'      => array(
+								'link' => '#111',
+							),
+							'typography' => array(
+								'fontSize' => '1em',
+							),
 						),
-						'typography' => array(
-							'fontSize' => '5em',
+						'core/heading/h2'     => array(
+							'color'      => array(
+								'link' => '#222',
+							),
+							'typography' => array(
+								'fontSize' => '2em',
+							),
 						),
-					),
-					'core/query-title/h4' => array(
-						'color'      => array(
-							'link' => '#444',
+						'core/post-title/h2'  => array(
+							'color'      => array(
+								'link' => '#222',
+							),
+							'typography' => array(
+								'fontSize' => '2em',
+							),
 						),
-						'typography' => array(
-							'fontSize' => '4em',
+						'core/post-title/h5'  => array(
+							'color'      => array(
+								'link' => '#555',
+							),
+							'typography' => array(
+								'fontSize' => '5em',
+							),
 						),
-					),
-					'core/query-title/h5' => array(
-						'color'      => array(
-							'link' => '#555',
+						'core/query-title/h4' => array(
+							'color'      => array(
+								'link' => '#444',
+							),
+							'typography' => array(
+								'fontSize' => '4em',
+							),
 						),
-						'typography' => array(
-							'fontSize' => '5em',
+						'core/query-title/h5' => array(
+							'color'      => array(
+								'link' => '#555',
+							),
+							'typography' => array(
+								'fontSize' => '5em',
+							),
 						),
 					),
-				),
-				'misc'     => 'value',
-			)
+					'misc'     => 'value',
+				)
+			),
+			'core'
 		);
 
 		$this->assertEquals(
diff --git a/phpunit/class-wp-theme-json-test.php b/phpunit/class-wp-theme-json-test.php
index 769fc8c0011db..c38aa1d9ae768 100644
--- a/phpunit/class-wp-theme-json-test.php
+++ b/phpunit/class-wp-theme-json-test.php
@@ -57,107 +57,111 @@ function test_get_settings() {
 	}
 
 	function test_get_stylesheet() {
-		$theme_json = new WP_Theme_JSON_Gutenberg(
-			array(
-				'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
-				'settings' => array(
-					'color'      => array(
-						'text'    => 'value',
-						'palette' => array(
-							array(
-								'slug'  => 'grey',
-								'color' => 'grey',
+		$theme_json = new WP_Theme_JSON_Gutenberg( array() );
+		$theme_json->merge(
+			new WP_Theme_JSON_Gutenberg(
+				array(
+					'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
+					'settings' => array(
+						'color'      => array(
+							'text'    => 'value',
+							'palette' => array(
+								array(
+									'slug'  => 'grey',
+									'color' => 'grey',
+								),
 							),
 						),
-					),
-					'typography' => array(
-						'fontFamilies' => array(
-							array(
-								'slug'       => 'small',
-								'fontFamily' => '14px',
-							),
-							array(
-								'slug'       => 'big',
-								'fontFamily' => '41px',
+						'typography' => array(
+							'fontFamilies' => array(
+								array(
+									'slug'       => 'small',
+									'fontFamily' => '14px',
+								),
+								array(
+									'slug'       => 'big',
+									'fontFamily' => '41px',
+								),
 							),
 						),
-					),
-					'misc'       => 'value',
-					'blocks'     => array(
-						'core/group' => array(
-							'custom' => array(
-								'base-font'   => 16,
-								'line-height' => array(
-									'small'  => 1.2,
-									'medium' => 1.4,
-									'large'  => 1.8,
+						'misc'       => 'value',
+						'blocks'     => array(
+							'core/group' => array(
+								'custom' => array(
+									'base-font'   => 16,
+									'line-height' => array(
+										'small'  => 1.2,
+										'medium' => 1.4,
+										'large'  => 1.8,
+									),
 								),
 							),
 						),
 					),
-				),
-				'styles'   => array(
-					'color'    => array(
-						'text' => 'var:preset|color|grey',
-					),
-					'misc'     => 'value',
-					'elements' => array(
-						'link' => array(
-							'color' => array(
-								'text'       => '#111',
-								'background' => '#333',
-							),
+					'styles'   => array(
+						'color'    => array(
+							'text' => 'var:preset|color|grey',
 						),
-					),
-					'blocks'   => array(
-						'core/group'     => array(
-							'elements' => array(
-								'link' => array(
-									'color' => array(
-										'text' => '#111',
-									),
-								),
-							),
-							'spacing'  => array(
-								'padding' => array(
-									'top'    => '12px',
-									'bottom' => '24px',
+						'misc'     => 'value',
+						'elements' => array(
+							'link' => array(
+								'color' => array(
+									'text'       => '#111',
+									'background' => '#333',
 								),
 							),
 						),
-						'core/heading'   => array(
-							'color'    => array(
-								'text' => '#123456',
-							),
-							'elements' => array(
-								'link' => array(
-									'color'      => array(
-										'text'       => '#111',
-										'background' => '#333',
+						'blocks'   => array(
+							'core/group'     => array(
+								'elements' => array(
+									'link' => array(
+										'color' => array(
+											'text' => '#111',
+										),
 									),
-									'typography' => array(
-										'fontSize' => '60px',
+								),
+								'spacing'  => array(
+									'padding' => array(
+										'top'    => '12px',
+										'bottom' => '24px',
 									),
 								),
 							),
-						),
-						'core/post-date' => array(
-							'color'    => array(
-								'text' => '#123456',
+							'core/heading'   => array(
+								'color'    => array(
+									'text' => '#123456',
+								),
+								'elements' => array(
+									'link' => array(
+										'color'      => array(
+											'text'       => '#111',
+											'background' => '#333',
+										),
+										'typography' => array(
+											'fontSize' => '60px',
+										),
+									),
+								),
 							),
-							'elements' => array(
-								'link' => array(
-									'color' => array(
-										'background' => '#777',
-										'text'       => '#555',
+							'core/post-date' => array(
+								'color'    => array(
+									'text' => '#123456',
+								),
+								'elements' => array(
+									'link' => array(
+										'color' => array(
+											'background' => '#777',
+											'text'       => '#555',
+										),
 									),
 								),
 							),
 						),
 					),
-				),
-				'misc'     => 'value',
-			)
+					'misc'     => 'value',
+				)
+			),
+			'core'
 		);
 
 		$this->assertEquals(
@@ -175,24 +179,28 @@ function test_get_stylesheet() {
 	}
 
 	function test_get_stylesheet_preset_classes_work_with_compounded_selectors() {
-		$theme_json = new WP_Theme_JSON_Gutenberg(
-			array(
-				'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
-				'settings' => array(
-					'blocks' => array(
-						'core/heading' => array(
-							'color' => array(
-								'palette' => array(
-									array(
-										'slug'  => 'white',
-										'color' => '#fff',
+		$theme_json = new WP_Theme_JSON_Gutenberg( array() );
+		$theme_json->merge(
+			new WP_Theme_JSON_Gutenberg(
+				array(
+					'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
+					'settings' => array(
+						'blocks' => array(
+							'core/heading' => array(
+								'color' => array(
+									'palette' => array(
+										array(
+											'slug'  => 'white',
+											'color' => '#fff',
+										),
 									),
 								),
 							),
 						),
 					),
-				),
-			)
+				)
+			),
+			'theme'
 		);
 
 		$this->assertEquals(
@@ -202,33 +210,37 @@ function test_get_stylesheet_preset_classes_work_with_compounded_selectors() {
 	}
 
 	function test_get_stylesheet_preset_rules_come_after_block_rules() {
-		$theme_json = new WP_Theme_JSON_Gutenberg(
-			array(
-				'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
-				'settings' => array(
-					'blocks' => array(
-						'core/group' => array(
-							'color' => array(
-								'palette' => array(
-									array(
-										'slug'  => 'grey',
-										'color' => 'grey',
+		$theme_json = new WP_Theme_JSON_Gutenberg( array() );
+		$theme_json->merge(
+			new WP_Theme_JSON_Gutenberg(
+				array(
+					'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
+					'settings' => array(
+						'blocks' => array(
+							'core/group' => array(
+								'color' => array(
+									'palette' => array(
+										array(
+											'slug'  => 'grey',
+											'color' => 'grey',
+										),
 									),
 								),
 							),
 						),
 					),
-				),
-				'styles'   => array(
-					'blocks' => array(
-						'core/group' => array(
-							'color' => array(
-								'text' => 'red',
+					'styles'   => array(
+						'blocks' => array(
+							'core/group' => array(
+								'color' => array(
+									'text' => 'red',
+								),
 							),
 						),
 					),
-				),
-			)
+				)
+			),
+			'theme'
 		);
 
 		$this->assertEquals(
@@ -242,34 +254,38 @@ function test_get_stylesheet_preset_rules_come_after_block_rules() {
 	}
 
 	public function test_get_stylesheet_preset_values_are_marked_as_important() {
-		$theme_json = new WP_Theme_JSON_Gutenberg(
-			array(
-				'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
-				'settings' => array(
-					'color' => array(
-						'palette' => array(
-							array(
-								'slug'  => 'grey',
-								'color' => 'grey',
+		$theme_json = new WP_Theme_JSON_Gutenberg( array() );
+		$theme_json->merge(
+			new WP_Theme_JSON_Gutenberg(
+				array(
+					'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
+					'settings' => array(
+						'color' => array(
+							'palette' => array(
+								array(
+									'slug'  => 'grey',
+									'color' => 'grey',
+								),
 							),
 						),
 					),
-				),
-				'styles'   => array(
-					'blocks' => array(
-						'core/paragraph' => array(
-							'color'      => array(
-								'text'       => 'red',
-								'background' => 'blue',
-							),
-							'typography' => array(
-								'fontSize'   => '12px',
-								'lineHeight' => '1.3',
+					'styles'   => array(
+						'blocks' => array(
+							'core/paragraph' => array(
+								'color'      => array(
+									'text'       => 'red',
+									'background' => 'blue',
+								),
+								'typography' => array(
+									'fontSize'   => '12px',
+									'lineHeight' => '1.3',
+								),
 							),
 						),
 					),
-				),
-			)
+				)
+			),
+			'core'
 		);
 
 		$this->assertEquals(
@@ -279,35 +295,42 @@ public function test_get_stylesheet_preset_values_are_marked_as_important() {
 	}
 
 	public function test_merge_incoming_data() {
-		$initial = array(
-			'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
-			'settings' => array(
-				'color'  => array(
-					'custom'  => false,
-					'palette' => array(
-						array(
-							'slug'  => 'red',
-							'color' => 'red',
+		$theme_json = new WP_Theme_JSON_Gutenberg( array() );
+		$theme_json->merge(
+			new WP_Theme_JSON_Gutenberg(
+				array(
+					'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
+					'settings' => array(
+						'color'  => array(
+							'custom'  => false,
+							'palette' => array(
+								array(
+									'slug'  => 'red',
+									'color' => 'red',
+								),
+								array(
+									'slug'  => 'green',
+									'color' => 'green',
+								),
+							),
 						),
-						array(
-							'slug'  => 'green',
-							'color' => 'green',
+						'blocks' => array(
+							'core/paragraph' => array(
+								'color' => array(
+									'custom' => false,
+								),
+							),
 						),
 					),
-				),
-				'blocks' => array(
-					'core/paragraph' => array(
-						'color' => array(
-							'custom' => false,
+					'styles'   => array(
+						'typography' => array(
+							'fontSize' => '12',
 						),
 					),
-				),
-			),
-			'styles'   => array(
-				'typography' => array(
-					'fontSize' => '12',
-				),
+
+				)
 			),
+			'core'
 		);
 
 		$add_new_block = array(
@@ -437,29 +460,37 @@ public function test_merge_incoming_data() {
 					'custom'         => true,
 					'customGradient' => true,
 					'palette'        => array(
-						array(
-							'slug'  => 'blue',
-							'color' => 'blue',
+						'core' => array(
+							array(
+								'slug'  => 'blue',
+								'color' => 'blue',
+							),
 						),
 					),
 					'gradients'      => array(
-						array(
-							'slug'     => 'gradient',
-							'gradient' => 'gradient',
+						'core' => array(
+							array(
+								'slug'     => 'gradient',
+								'gradient' => 'gradient',
+							),
 						),
 					),
 				),
 				'typography' => array(
 					'fontSizes'    => array(
-						array(
-							'slug' => 'fontSize',
-							'size' => 'fontSize',
+						'core' => array(
+							array(
+								'slug' => 'fontSize',
+								'size' => 'fontSize',
+							),
 						),
 					),
 					'fontFamilies' => array(
-						array(
-							'slug'       => 'fontFamily',
-							'fontFamily' => 'fontFamily',
+						'core' => array(
+							array(
+								'slug'       => 'fontFamily',
+								'fontFamily' => 'fontFamily',
+							),
 						),
 					),
 				),
@@ -501,14 +532,13 @@ public function test_merge_incoming_data() {
 			),
 		);
 
-		$theme_json = new WP_Theme_JSON_Gutenberg( $initial );
-		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_new_block ) );
-		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_key_in_settings ) );
-		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $update_key_in_settings ) );
-		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_styles ) );
-		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_key_in_styles ) );
-		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_invalid_context ) );
-		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $update_presets ) );
+		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_new_block ), 'core' );
+		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_key_in_settings ), 'core' );
+		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $update_key_in_settings ), 'core' );
+		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_styles ), 'core' );
+		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_key_in_styles ), 'core' );
+		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $add_invalid_context ), 'core' );
+		$theme_json->merge( new WP_Theme_JSON_Gutenberg( $update_presets ), 'core' );
 		$actual = $theme_json->get_raw_data();
 
 		$this->assertEqualSetsWithIndex( $expected, $actual );