The material class.

This class exposes all properties from a material, allowing you to animate them. You can also use it to set custom shader properties that can't be accessed through the inspector (e.g. matrices).

In order to get the material used by an object, use the Renderer.material property: See Also: Materials, ShaderLab documentation.

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

public class Example(MonoBehaviour):

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