I don't know about anyone else but I have a TERRIBLE time 
mixing colors in hopes of creating this "one certain color that would make the cookies killer". I found a tool that has helped me a bunch. It's called the Color Mixing Guide from Magic Palette. I happened across it in the art section of Hobby Lobby. It's a chart that shows how to mix over 300 colors using 18 base colors. Yes, it's based on artist paint color but I've found my Americolor colorings are pretty close to the artist paint color. It's a little pricey so you'll want to use a coupon to purchase. Hope this helps some other color-challenged cookie makers! 
http://www.kitchengifts.com/colorchart.html
Here is a color mixing chart from the fabulous website kitchengifts. This chart has helped me a lot, and hope it helps you too!
Quote by @%username% on %date%
%body%