After I discovered one of the cockroaches was white and it's old skin was in the container I checked on them more frequently that day. The white one got darker and darker all day. By the next day it was almost all the way brown again with white spots. The most curious thing though was that the skin that was shed started disappearing throughout the day and I found the white cockroach near it at one point. I think it may have eaten the old skin because it was half gone by that night and all the way gone by the next day.