UI BUTTON Change Color On Click HELP PLEASE!!

I have this javascript code:

var button : UI.Button;

function Start()
 function CallMePlease()
     print("Button surely was clicked");

Now what i want is when i call the function CallMePlease that the color of the button changes to example red. Please im losing my mind here. I can’t find the tutorial ANYWHERE!! Im using Unity 5.

button.color = Color.red;

Does this not work?