What kind of paint do I need to paint rubber?
Instead of painting pucks why not just order colored ones?

http://www.ministicks.com/colored_hockey_pucks_and_colored_foam_hockey_pucks_s/14687.htm

This page has 4 different colors for regulation pucks, and 8 colors for regulation size foam pucks.  

This was my first search and I'm sure you could find others if you needed something specific.