Material.color  

// Fade the color from red to green
// back and forth over the defined duration

var colorStart : Color = Color.red;
var colorEnd : Color = Color.green;
var duration : float = 1.0;

function Update () {
    var lerp : float = Mathf.PingPong (Time.time, duration) / duration;
    renderer.material.color = Color.Lerp (colorStart, colorEnd, lerp);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Color colorStart = Color.red;
    public Color colorEnd = Color.green;
    public float duration = 1.0F;
    void Update() {
        float lerp = Mathf.PingPong(Time.time, duration) / duration;
        renderer.material.color = Color.Lerp(colorStart, colorEnd, lerp);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public colorStart as Color = Color.red

    public colorEnd as Color = Color.green

    public duration as single = 1.0F

    def Update():
        lerp as single = (Mathf.PingPong(Time.time, duration) / duration)
        renderer.material.color = Color.Lerp(colorStart, colorEnd, lerp)