Greetings from LA, where I've been workshopping a new opera by USC composer, Donald Crockett. It's called The Face. The music is beautiful, my colleagues are excellent and very fun, and the weather has been pretty much flawless.
In oratorio, I think it looks nice if all the singers are holding the same color scores. Since my Carmina Burana vocal score is slightly oversized and would therefore look weird and be unstable if I tried to jam it into a black binder, I just covered the thing with black "duck" tape for my recent performance in Columbus, Georgia. It looks fine from the audience, and gives the score a nice rubbery grippy quality (unlike some black binders which can get slippery in sweaty hands).