// Paint red the collider we hit.
function OnControllerColliderHit(hit : ControllerColliderHit) {
    hit.collider.renderer.material.color = Color.red;
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void OnControllerColliderHit(ControllerColliderHit hit) {
        hit.collider.renderer.material.color = Color.red;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def OnControllerColliderHit(hit as ControllerColliderHit):
        hit.collider.renderer.material.color = Color.red