Well yes to those that say that our vision is limited by the spectrum of light that is true but theres more too it than that. Its how your brain categorizes and classifies those spectrums and how many rods and cones you have in your eyes. Dogs can only perceive two primary colors and a mantis shrimp can see 17. That being said since you are not really using your actual pysical eyes in a dream what really matters is brain structure rather than rods cones or the actuall color spectrum which we cant see all of. Our brains are plastic meaning they can change with surprising ease. So with practice its more than possible to see another color if you try hard. It will probably be hard to recall at first though. Also I think when people say oh it was kinda like this color and that color what they mean is like the way orang is kinda red and sorta yellow but its its own thing. I mean just because it happens in real life dosnt mean that its not possible. Take thresixty vision there are lots of reports on that but do all of those people have eyes in the back of their head? no of course not. Blind people who have been blind lifelong have dreams with color and shape they may be vague or mind blowing but they happen. Your brein is pretty flexible. The only limitation you would face is subconsiously convincing yourself that you cant do it by dismissing the thought before trying.
Happy dreaming,
Eesiel