I am using a green plastic egg, and an orange one at the moment. Doesn't seem to bother them. In fact, if I take one out it is invariably the nest with the plastic egg that gets the daily offerings from the girls. Of course, the newest girls haven't started yet. I may be singing a different song in AugustGood to know that works! I was wondering if the really bright colors would throw the chickens off or not. But come to think of it do chickens even see color?