GUIStyle.active

Description

Rendering settings for when the control is pressed down.

using UnityEngine;

public class Example : MonoBehaviour
{
    // Assigns a texture to button for when the control
    // is pressed down

    Texture2D aTexture;

    void OnGUI()
    {
        if (!aTexture)
        {
            Debug.LogError("Assign a texture on the editor first");
            return;
        }

        GUI.skin.button.active.background = aTexture;
    }
}