i actually have a set of these apart already at home that i have been looking to play with. They are a real pain in the ass to open due to he type of glue that they use.
the Light bars on the top are illuminated by 3 sets of LED's and i believe they are Lumileds Luxeon FX Plus LED's. They are crazy small though, only 1.6mm and there are 4 of them in a grouping. The headlight i had was used (and cheep) and has 4 of these burned out.
This particular LED only comes in white and Amber however, so unless you were going to paint the inside the the headlgiht to change it that would be the only option, and it would be dimmer.
There are other LED's similar size from Cree, however the solder pad on them is different so it would not be practical to use, but they come in assorted colors