I've recently done an Optima shell.
http://www.oople.com/forums/showthread.php?t=147090
I used Createx Opaque Yellow 5204 and mixed it to warm it up with Createx Opaque Red 5210. You have to test it out a little, trim out some old coke bottles. I got it really orange at first which was way to much, so you only have to drop in a small amount.
Hope this is useful!