diff --git a/examples/healpix.cpp b/examples/healpix.cpp
index 98e6be93..0aa94cc0 100644
--- a/examples/healpix.cpp
+++ b/examples/healpix.cpp
@@ -16,6 +16,7 @@ int main (int argc, char** argv)
 
     auto hpv = std::make_unique<morph::HealpixVisual<float>> (morph::vec<float>{0,0,0});
     v.bindmodel (hpv);
+    hpv->indicate_axes = true;
     hpv->set_order (ord);
     hpv->cm.setType (morph::ColourMapType::Plasma);
 
diff --git a/morph/CoordArrows.h b/morph/CoordArrows.h
index ed8912f1..f4fb513d 100644
--- a/morph/CoordArrows.h
+++ b/morph/CoordArrows.h
@@ -13,6 +13,7 @@
 #include <morph/VisualModel.h>
 #include <morph/mathconst.h>
 #include <morph/VisualTextModel.h>
+#include <morph/colour.h>
 #include <array>
 
 namespace morph {
@@ -146,9 +147,9 @@ namespace morph {
 
         //! The colours of the arrows, and of the centre sphere
         std::array<float, 3> centresphere_col = {1.0f, 1.0f, 1.0f};
-        std::array<float, 3> x_axis_col = {1.0f, 0.0f, 0.0f}; // Red
-        std::array<float, 3> y_axis_col = {0.0f, 1.0f, 0.0f}; // Green
-        std::array<float, 3> z_axis_col = {0.0f, 0.0f, 1.0f}; // Blue
+        std::array<float, 3> x_axis_col = morph::colour::crimson;
+        std::array<float, 3> y_axis_col = morph::colour::springgreen2;
+        std::array<float, 3> z_axis_col = morph::colour::blue2;
 
         std::string x_label = "X";
         std::string y_label = "Y";
diff --git a/morph/HealpixVisual.h b/morph/HealpixVisual.h
index 4011e9fc..296086f5 100644
--- a/morph/HealpixVisual.h
+++ b/morph/HealpixVisual.h
@@ -33,8 +33,12 @@ namespace morph {
 
         void updateColours()
         {
-            this->vertexColors.clear(); // could potentially just replace values
             size_t n_data = this->n_pixels();
+
+            if (this->vertexColors.size() < n_data * 3) {
+                throw std::runtime_error ("vertexColors is not big enough to updateColours()");
+            }
+
             // Scale data
             morph::vvec<float> scaled_data (this->pixeldata);
             if (this->colourScale.do_autoscale == true) { this->colourScale.reset(); }
@@ -43,7 +47,9 @@ namespace morph {
             // Re-colour
             for (size_t i = 0u; i < n_data; ++i) {
                 auto c = this->cm.convert (scaled_data[i]);
-                this->vertex_push (c, this->vertexColors);
+                this->vertexColors[3*i] = c[0];
+                this->vertexColors[3*i+1] = c[1];
+                this->vertexColors[3*i+2] = c[2];
             }
 
             // Lastly, this call copies vertexColors (etc) into the OpenGL memory space
@@ -423,6 +429,30 @@ namespace morph {
             if (this->k == 0) { return; }
             this->healpix_triangles_by_nest();
             if (this->show_spheres == true) { this->vertex_spheres(); }
+            if (this->indicate_axes == true) { this->draw_coordaxes(); }
+        }
+
+        // Draw a small set of coordinate arrows with origin at pixel 0
+        void draw_coordaxes()
+        {
+            morph::vec<float> vpf0 = {0, 0, this->r};
+
+            // draw tubes
+            float tlen = this->r * 0.1f;
+            float tlen2 = this->r * 0.05f;
+            float tthk = this->r * 0.005f;
+
+            this->computeCone (vpf0 + (this->uz * tthk/2),
+                               vpf0 + (this->uz * tlen),
+                               0.0f, morph::colour::blue2, tthk);
+
+            this->computeCone (vpf0 + this->ux * tthk * 1.1f + this->uz * tthk,
+                               vpf0 + this->ux * tlen2 + this->uz * tthk,
+                               0.0f, morph::colour::crimson, tthk/2);
+
+            this->computeCone (vpf0 + this->uy * tthk * 1.1f + this->uz * tthk,
+                               vpf0 + this->uy * tlen2 + this->uz * tthk,
+                               0.0f, morph::colour::springgreen2, tthk/2);
         }
 
         int64_t n_pixels() { return 12 * this->nside * this->nside; }
@@ -480,6 +510,9 @@ namespace morph {
         // Show spheres at face locations? (mainly for debug)
         bool show_face_spheres = false;
 
+        // Show a little coordinate axes set indicating directions?
+        bool indicate_axes = false;
+
     private:
         // How many sides for the healpix? This is a choice of the user. Default to 3.
         int64_t k = 3; // k is the 'order'
diff --git a/morph/VisualModel.h b/morph/VisualModel.h
index ea2c13e2..0c91c16c 100644
--- a/morph/VisualModel.h
+++ b/morph/VisualModel.h
@@ -505,6 +505,8 @@ namespace morph {
 
         //! Get mv_offset in a json-friendly string
         std::string translation_str() { return this->mv_offset.str_mat(); }
+        //! And a simple getter for mv_offset
+        vec<float> get_mv_offset() { return this->mv_offset; }
 
         //! Return the number of elements in this->indices
         std::size_t indices_size() { return this->indices.size(); }