Some block patterns don't respect the theme color palette and look out of place or broken

[fullofcaffeine]

Describe the bug

Some block patterns have hardcoded color values and don't follow the theme palette, causing them to look out of place or broken when used from some themes.

I've found the following blocks seem to have hardcoded values by adding them to a dark them (Rivington):

• Two columns of text
• Two columns of text with images
• Three columns of text with buttons
• Heading and Paragraph

The blocks above will probably look broken under darker themes.

I'm not sure about the following blocks as they look okay under Rivington, but I suspect they also have hardcoded color values:

• Large header with a heading and a button
• Large header with a heading
• Three buttons
• Two buttons

To reproduce
Steps to reproduce the behavior:

1. Install and activate Gutenberg 8.7 in your WordPress instance;
2. Install and activate a dark theme, e.g. Coral Dark;
3. Add a new post;
4. Add any of the block patterns listed above to the page and observe how they look out of place or broken visually.

Expected behavior

The blocks get the right color values from the theme and blend in nicely.

Screenshots

Two columns of text	Two columns of text with images	Three columns of text with buttons	Heading and Paragraph	Large header with a heading and a button	Three buttons	Two buttons

Editor version (please complete the following information):

• WordPress version: 5.4.2
• Does the website has Gutenberg plugin installed, or is it using the block editor that comes by default? gutenberg plugin
• If the Gutenberg plugin is installed, which version is it? 8.7

Desktop (please complete the following information):

• OS: Linux Mint 18.04
• Browser: Firefox Quantum 80.0b4