Scripting Reference
Component.renderer

var renderer : Renderer

Description

The Renderer attached to this GameObject (null if there is none attached).

JavaScript 
renderer.material.color = Color.red;
using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        renderer.material.color = Color.red;
    }
}
import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        renderer.material.color = Color.red