My fish change color when pregnant, which appears to be a function of stretching of the belly region. Why you would get orange doesn't make sense to me. Do you have a picture? I wouldn't know what it is off the top of my head, but if you could provide a picture, maybe someone can take a look and see. I just wouldn't want it to be any kind of sign of illness. I don't want to frighten you. It doesn't sound like anything I've read about or seen myself, but if it's a new thing, show us a picture and maybe we can figure it out.