// Fades the red component of the material to zero 
// while the mouse is over the mesh

function OnMouseOver () {
    renderer.material.color -= Color(0.1, 0, 0) * Time.deltaTime;
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void OnMouseOver() {
        renderer.material.color -= new Color(0.1F, 0, 0) * Time.deltaTime;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def OnMouseOver():
        renderer.material.color -= (Color(0.1F, 0, 0) * Time.deltaTime)