GUISkin.toggle  

// Modifies only the toggle style of the current GUISkin

var style : GUIStyle;
private var val : boolean = false;

function OnGUI() {
    GUI.skin.toggle = style;
    val = GUILayout.Toggle(val,"A Toggle control");
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public GUIStyle style;
    private bool val = false;
    void OnGUI() {
        GUI.skin.toggle = style;
        val = GUILayout.Toggle(val, "A Toggle control");
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public style as GUIStyle

    private val as bool = false

    def OnGUI():
        GUI.skin.toggle = style
        val = GUILayout.Toggle(val, 'A Toggle control')