I had to answer the question of whether adhesive-backed vinyl could be painted successfully before cutting. I'm using WR-LPU topcoat, a marine coating. The surface of the vinyl was sanded first and cleaned with a damp rag before painting. I mixed primary colors to make the desired colour. I was attempting fuscia but ended up close, but not quite there.
This picture shows the result after I stuck the letters onto some clear vinyl.
So, the home crafter can now attain just about any color of adhesive backed vinyl with a little bit of paint mixing. It would be great if System Three made "cool" primaries like light lemon yellow and a lighter blue, or CMYK primaries so home paint mixing would yield a greater range of colors. In my acrylic painting course we had three "cool" primaries and three "warm" primaries, and along with black and white, were all the colours needed to mix any desired colour.