Unity OnGUI how to change color, transparency and font

Here is what I found after googling for a while

1. On your unity, ASSETS -> CREATE -> GUISKIN, name it "myGUISKIN"
2. On your script, create a new variable

var myskin : GUISkin ;

function OnGUI () 

{

    GUI.skin = myGUISkin;

}

3. Drag your script to one of the object, then drag your myGUISKIN into your script variable "myskin"
4. Now you can configure everything on your myGUISKIN, you can change the background color, you can change the font size and everything you can think of