I also love it when an sorority's color(s) and/or official jewel(s) are in a badge, but I think it's also cool to get colors of your alma mater.
This Pi Phi badge gives me some serious badge envy...
I can't seem to find a pic from HJ, but I think the ADPi badge in white gold with aquamarines is gorgeous.
I don't like Theta badges with colored stones because I think it detracts from the black and gold simplicity. I think it's as beautiful plain as it is with diamonds and/or pearls!