diff --git a/colours.js b/colours.js
index 225a3b5..20513b5 100644
--- a/colours.js
+++ b/colours.js
@@ -1,14 +1,14 @@
 import ColorScheme from 'color-scheme';
 import Color from 'color';
 
-export const get_colours = (basis) => {
-        const colours = get_colours_spectrum(basis);
-        console.log(colours);
+export const get_colours = (basis, n) => {
+        const colours = get_colours_spectrum(basis, n);
         return colours;
 }
 
 
-const get_colours_tetrade = (basis) => {
+const get_colours_tetrade = (basis, n) => {
+        // this always returns what the scheme has so it ignores n
 	const basis_c = Color(basis);
 	const hslb = basis_c.hsl();
 	const hue = hslb['color'][0];
@@ -25,16 +25,16 @@ const get_colours_tetrade = (basis) => {
 }
 
 
-const get_colours_spectrum = (basis) => {
+const get_colours_spectrum = (basis, n) => {
+        // this returns n colours evenly spaced by hue
 	const basis_c = Color(basis);
 	const hslb = basis_c.hsl();
 	const hue = hslb['color'][0];
 	const saturation = hslb['color'][1];
 	const luminance = hslb['color'][2];
-        const SPECTRUM = 10;
         const hsl = [];
-        for( let i = 0; i < SPECTRUM; i++ ) {
-            const h = (hue + i * 360 / SPECTRUM) % 360;
+        for( let i = 0; i < n; i++ ) {
+            const h = (hue + i * 360 / n) % 360;
             hsl.push(Color.hsl(h, saturation, luminance));
         }
 	return hsl.map((hslc) => hslc.rgbNumber());
diff --git a/gui.js b/gui.js
index c92b570..163ad42 100644
--- a/gui.js
+++ b/gui.js
@@ -13,6 +13,7 @@ const DEFAULTS = {
 	inscribed: false,
 	inscribe_all: false,
 	colour: 0x3293a9,
+	colour_n: 5,
 	background: 0xd4d4d4,
 	hyperplane: 0.93,
 	zoom: 1,
diff --git a/main.js b/main.js
index 054683a..215bde8 100644
--- a/main.js
+++ b/main.js
@@ -66,9 +66,20 @@ document.body.appendChild( renderer.domElement );
 // set up colours and materials for gui callbacks
 
 scene.background = new THREE.Color(DEFAULTS.background);
-const node_colours = get_colours(DEFAULTS.colour);
 
 
+const STRUCTURES = POLYTOPES.build_all();
+
+const STRUCTURES_BY_NAME = {};
+
+STRUCTURES.map((s) => STRUCTURES_BY_NAME[s.name] = s);
+
+const max_ms = Math.max(...STRUCTURES.map((s) => s.colour_n));
+
+// make enough materials for the largest value of colour_n
+
+const node_colours = get_colours(DEFAULTS.colour, max_ms);
+
 const node_ms = node_colours.map((c) => new THREE.MeshStandardMaterial({color: c}));
 const link_ms = node_colours.map((c) => new THREE.MeshStandardMaterial({color: c}));
 
@@ -91,17 +102,11 @@ const face_ms = [
 	];
 
 for( const face_m of face_ms ) {
-	face_m.transparent = true;	
+	face_m.transparent = true;
 	face_m.opacity = FACE_OPACITY;
 }
 
 
-const STRUCTURES = POLYTOPES.build_all();
-
-const STRUCTURES_BY_NAME = {};
-
-STRUCTURES.map((s) => STRUCTURES_BY_NAME[s.name] = s);
-
 let shape = false;
 let structure = false;
 let node_show = [];
@@ -162,17 +167,20 @@ relnotes.addEventListener('click', releaseNotes);
 // change the colors.  Otherwise we just read stuff from gui.params.
 
 function setColours(c) {
-    const nc = get_colours(c);
-    for( let i = 0; i < node_ms.length; i++ ) {
-    	node_ms[i].color = new THREE.Color(nc[i]);
-    	link_ms[i].color = new THREE.Color(nc[i]);
-    }
-    if( shape ) {
-        // taperedLink.set_color updates according to the link index
-       shape.links.map((l) => l.object.set_colour(nc));
+    if( structure ) {
+        const nc = get_colours(c, structure.colour_n);
+        for( let i = 0; i < node_ms.length; i++ ) {
+        	node_ms[i].color = new THREE.Color(nc[i]);
+        	link_ms[i].color = new THREE.Color(nc[i]);
+        }
+        if( shape ) {
+            // taperedLink.set_color updates according to the link index
+            shape.links.map((l) => l.object.set_colour(nc));
+        }
     }
 }
 
+
 function setBackground(c) {
 	scene.background = new THREE.Color(c)
 }
diff --git a/polytopes.js b/polytopes.js
index 1defa51..241cc30 100644
--- a/polytopes.js
+++ b/polytopes.js
@@ -819,10 +819,6 @@ export const cell600_layered = () => {
 
 	// recolour nodes according to 24-cell partition
 
-        nodes.map((n) => n.label = 8 + plabels[n.id]); 
-
-        const node_c = [ 8, 9, 10, 11, 12, 13, 14, 15 ];
-
 	const options = [];
 	const layers = [];
 
@@ -831,7 +827,7 @@ export const cell600_layered = () => {
 		options.push({
 			name: CELLINDEX.LAYER_NAMES[i],
 			links: [...layers],
-			nodes: [...node_c, ...layers]
+			nodes: [...layers]
 		})
 	}
 
@@ -1075,7 +1071,7 @@ export const icosahedron = () => {
 
 
 export const build_all = () => {
-	return [
+	const shapes = [
 		tetrahedron(),
 		octahedron(),
 		cube(),
@@ -1092,13 +1088,17 @@ export const build_all = () => {
 	 	cell120_inscribed_cell5(),
 	 	cell120_layered()
 	 	];
+        for( const shape of shapes ) {
+            shape.colour_n = count_labels(shape);
+        }
+        return shapes;
 }
 
 export const count_labels = (shape) => {
     const labels = {};
     shape.nodes.map((n) => labels[n.label] = true);
     shape.links.map((n) => labels[n.label] = true);
-    return Object.keys(labels);
+    return Object.keys(labels).length;
 };
 
 export const radii = (shape) => {