How to make a GUI that isnt alpha transparent?

I’m trying to make a simple HELP screen and I would like to make the backgorund none-translusive aka alpha = 0.

I’ve tried with:

 GUI.color = new Color(1.0f , 0.0f , 0.0f , 1.0f);
 GUI.contentColor = new Color(0.0f , 1.0f , 0.0f , 1.0f); 
 GUI.backgroundColor = new Color(0.0f , 0.0f , 1.0f , 1.0f);

None of them seems to make the background/layer less transparent?

What have I missed?

The images themselves in the default skin are semitransparent. You’ll need different images.