Thanks for the info. Here is the link to the Weber site.
http://www.weberart.com/woil/index.html
They provide a pdf brochure of the product. The only thing I saw was that they put a big headline on the top of the brochure about mixing with acrylics, but then they only devote one minimally informative sentence about it. I also notices that most of their orange, red, yellow and blue colors are "hues."
It might be worth contacting the company directly to get more information about it so people that would want to mix the colors would have a better understanding of the rational and mechanics of mixing.