Change GUIStyle when Clicked

Hey guys i have a question, i made this code and when i click “earth” button it changes into “earthActive” with no problem, but when i click “earthActive” it doesnt change back to “earth”.

I dont know if i explain myself, when i click “earth” i want that the button stay in “earthActive” until i click it again, and then change back to “earth”

Here’s the code

#pragma strict
var HighBg : Texture;

var earth : GUIStyle;
var earthActive : GUIStyle;

function OnGUI(){
    GUI.DrawTexture (Rect(0,0,800,600), HighBg, ScaleMode.ScaleToFit, true);
    GameObject.Find("HOWTOPLAY").GetComponent(mainhowto).enabled = false;

    if (GUI.Button (Rect(100,100,91,31), "", earth)){
		earth = earthActive;
    }
}

Forget it guys i already solve it doing this:

#pragma strict
var HighBg : Texture;

var earth : GUIStyle;
var earthClicked : GUIStyle;
var earthisActive : boolean;

function OnGUI(){
    GUI.DrawTexture (Rect(0,0,800,600), HighBg, ScaleMode.ScaleToFit, true);
    GameObject.Find("HOWTOPLAY").GetComponent(mainhowto).enabled = false;

    if (GUI.Button (Rect(100,100,91,31), "", earth)){
		earthisActive = !earthisActive;
    }
    if(earthisActive){
    	GUI.Button (Rect(100,100,91,31), "", earthClicked);
    }
}