ChangeOnCollision.cs

using UnityEngine;
using System.Collections;

public class ChangeOnCollision : MonoBehaviour {

	private Material myMaterial;

	// Use this for initialization
	void Start () {
		myMaterial = GetComponent<Renderer>().material;
	}
	
	void onTriggerEnter(Collider other){
		myMaterial.color = Color.red;
	}
}