Change the texture of a GUI BUTTON

I’m trying to change the texture of a button, and i cant seem to figure out how to do it.

here is a sample of my code

if (GUILayout.Button ( square3, ("label") ) && (gameWin == false))
	if (whichSquare == 3) 
	gameWin = true ;            
	else if (whichSquare != 3)
	// change button texture to square3Wrong

use a private var that holds the current texture you give to the button. At start, initialiaze it with square3, when the button is pressed assing it the square3Wrong texture. While I’m at it, you shoul use { } with the if of your button.