Here’s the technique that I’m planning to use to track who’s in the light and who isn’t. I haven’t tested it yet, because I haven’t had a chance to play, but here it is.
I’m going to use poker chips. I’ll probably be using the red ones for Hit Points anyway, so that leaves me with blue and white. When somebody lights a torch (or whatever), they’ll get a number of white and blue tokens to match their light source. White for bright light, and blue for dim, and they can pass those out as they like.
I remember seeing someone post a “light mat” with zones marked for bright and dim light, and each player would put their token in the appropriate region. Maybe it was on G+? It looked pretty good, I’m going to do something similar.