I've used colored incandescents in a couple games. Reds work great. I'm about to get some blue 555s for my Embryon. Green wasn't all that effective. I used Green and Red in my FACES for the two Bonus count sequences and while the green makes a subtle difference, it's only very subtle, the red pops pretty nicely and looks great. I would imagine yellow might be a little weak too but don't have experience with it.