// Set main color to red
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

// Change renderer's material each changeInterval
// seconds from the material array defined in the inspector.

var materials : Material[];
var changeInterval = 0.33;

function Update () {
    if (materials.Length == 0) // do nothing if no materials
        return;

    // we want this material index now
    var index : int = Time.time / changeInterval;
    // take a modulo with materials count so that animation repeats
    index = index % materials.Length;
    // assign it to the renderer
    renderer.sharedMaterial = materials[index];
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Material[] materials;
    public float changeInterval = 0.33F;
    void Update() {
        if (materials.Length == 0)
            return;
        
        int index = Time.time / changeInterval;
        index = index % materials.Length;
        renderer.sharedMaterial = materials[index];
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public materials as (Material)

    public changeInterval as single = 0.33F

    def Update():
        if materials.Length == 0:
            return
        index as int = (Time.time / changeInterval)
        index = (index % materials.Length)
        renderer.sharedMaterial = materials[index]