actually, IME, the damsels we have had and seen, dull in dolor, almostt pale sometimes, when the lights go out, but after the lights go on, it comes back in several minutes, i think it is a chameleon like effect, to hide them from predators at night
I have done no actual studies, but this seems to be normal for many damsels(maybe even all), if i am wrong, i am sure someone will correct me soon
HTH