GUIStyle.active

Description

Rendering settings for when the control is pressed down.

	// Assigns a texture to button for when the control
	// is pressed down

	var aTexture : Texture2D;

	function OnGUI() {
	 	if(!aTexture) {
			Debug.LogError("Assign a texture on the editor first");
			return;
		}
		
		GUI.skin.button.active.background = aTexture;		
	}

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public Texture2D aTexture;
    void OnGUI() {
        if (!aTexture) {
            Debug.LogError("Assign a texture on the editor first");
            return;
        }
        GUI.skin.button.active.background = aTexture;
    }
}