Yes, cover it up with something dark, towel, t-shirt, whatever you can find that works. I ferment on a basement staircase and it's almost always dark. I still cover my fermeter just to be sure.
Yeah, I've used old black drapes, black T-shirts, even a black skirt that my swmbo didn't want anymore!
I cover my glass and even my platic bucket fermentors. I even cover my starters!