I have been working on an effect for the next animation project, to make a neon light flicker. First I made a separate drawing of the lights, the opposite color they would be when I put them on top of my background painting.
Putting this image on a separate layer in photoshop, i inverted the colors, so the black would be a bright white, and the other colors would be neon-looking.
i made a separate version of the background with the colors taken out, to use for the un-lit version. This way i can make the neon appear to flicker when it is animated, alternating between the two versions.
oh, and i have been playing with some lighting effects for the other parts of the room, too.