One of the many things that I have learned about paint in resin is that it looks very different depending on the background.  One absolutely MUST experiment with colored resin on various backgrounds.  

  I generally paint my panels and canvas with white gesso.  But sometimes I go with black.  The black does a very different thing than the white does.  So one must experiment.  Try a dab of the resin with paint mixed in it on hardboard and see what color is revealed.

  For example, transparent iron oxide looks orange not red when on a black gesso background.  See, Looking Down #1 and #2.

  So, give experimenting a shot before pouring a full piece.  You will be glad that you did.