The trade name of the cel-vinyl paints used in the cartoon biz is 'Cartoon
Colors', I think.  We used them in medical illustration school for
animation.  You use cels which are punched along the top with registration
holes, and can stack them to see through the layers.

In the Bay Area they can be had at Gasser's photo supply, or at least they
could a couple of years ago.

Paint your outline on the front, and back paint with color.  The colors are
very homogeneous, and show no brush strokes.  I don't know where to get
cartoon colors--start at Flax's and go from there!

Bye for now,
Chris