When I bought my dip kit, they only had one size. Mine was $99 plus $18 shipping and came with 1 meter of film. I just checked out their website and it looks like the kit similar to the one I got is now only $69.
Not all of the films have clear parts where the painted parts with show through, but I think most do. The description of each film should tell you or maybe call them to be sure. They also seem to have more choices of film designs now than when I got mine. But, yes, if you get a film that has a clear background, whatever color you paint your parts, will show through that color. On my son's video game controller, we painted that red.