Drew,
Yes you can mix viynl, but I've never found a need to. They have around 30 different colors. Just like the powder coat, local stores only carry a few colors. Buy it on line and you'll lots of options.
I buy mine from Barlows.
http://www.barlowstackle.com/-Vinyl-Fishing-Lure-Paint-Regular-Colors--P960C132.aspx
This will show you all the different powder and viynl colors.
http://www.csipaint.com/products/