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 built-in Shaders don't display vertex colors. Use one that does, such as a Particle Shader, to see vertex colors)

using UnityEngine;

public class ExampleClass : MonoBehaviour
{
    void Start()
    {
        Mesh mesh = GetComponent<MeshFilter>().mesh;
        Vector3[] vertices = mesh.vertices;

        // create new colors array where the colors will be created.
        Color[] colors = new Color[vertices.Length];

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

        // assign the array of colors to the Mesh.
        mesh.colors = colors;
    }
}

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