Fraternity letters?
 

I'm about to purchase a letter shirt for my friend in a fraternity. His fraternity colors are purple and gold, so I was thinking a black shirt, purple background for the letters and black foreground. What do you think? Any other ideas?

Which Council?
 

What fraternity is he in?

You might want to look at websites that already cater to selling fraternity-specific clothing. I have friends in a fraternity with the same colors and I know they usually wear purple shirts.

http://www.s4g.com/

This is one of the best sites I've seen.