I'm pretty sure that that background does not have so much to do with it as the hardness in the water does. I used to have white rocks (white clown puke as some would call it), the discus were very skittish and hid most of the time. I read online that they are from dark waters in the amazon and that the bright sand is very hard on their eyes. As soon as I made the change to black sand, within minutes they changed 180 degrees and were as friendly as the cats I have. Also, I've witnessed them as vibrant as others and as black as others too. I've found that how they feel is how they look. After a water change they are as bright as ever or right when I wake up and they are hungry. When the water is old and needs a change or when they are angry and fighting, or right when they fall asleep, they are much darker in general. But the peppering was there when I had bright white and blue background and substrate and it stayed when I made the change to black for both.