How i colourize a Button and change the Font Size of it ?

Hey community

I wanna change the colour of the Button and the Font Size of the Button.

But how. I googled but I landed here.

My Code :

function OnGUI () {

//(position.width, position height, scale.width, scale.height)
if (GUI.Button (Rect (Screen.width / 5, Screen.height / 1.3, Screen.width / 6,Screen.height / 7), textPlay )) {
	 
	}
if (GUI.Button (Rect (Screen.width / 2.6, Screen.height / 1.3, Screen.width / 6,Screen.height / 7), textHowtoPlay )) {
	  
	}
if (GUI.Button (Rect (Screen.width / 1.5, Screen.height / 1.3, Screen.width / 6,Screen.height / 7), textExit )) {
	 Application.Quit();
	}
}

Thanks Before

Shame google did not take you to the documentation for Unity: