Mesh.colors

Description

Vertex colors of the mesh.

If no vertex colors are available an empty array will be returned.

	// Sets the vertex color to be red at the y=0 and green at y=1.
	// (Note that most builtin shaders don't display vertex colors, you can
	// use eg. a particle shader to see vertex colors)

	function Start () {
		var mesh : Mesh = GetComponent.<MeshFilter>().mesh;
		var vertices : Vector3[] = mesh.vertices;
		var colors : Color[] = new Color[vertices.Length];

		for (var i = 0; i < vertices.Length;i++)
			colors[i] = Color.Lerp(Color.red, Color.green, vertices[i].y);

		mesh.colors = colors;
	}

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void Start() {
        Mesh mesh = GetComponent<MeshFilter>().mesh;
        Vector3[] vertices = mesh.vertices;
        Color[] colors = new Color[vertices.Length];
        int i = 0;
        while (i < vertices.Length) {
            colors[i] = Color.Lerp(Color.red, Color.green, vertices[i].y);
            i++;
        }
        mesh.colors = colors;
    }
}

For performance reasons, consider using colors32 instead. This will avoid byte-to-float conversions in colors, as well as use less temporary memory.