There are a great many reasons Blood Parrots(BP's) can range in colors.
-Quality of the BP. Many LFS are selling low grade BP's whose colors tend to fade.
-Being dyed. If dyed at any time in their life their overall health as well as their natural color will be affected.
-Water parameters, stress. If your water parameters are off or the fish is stressed from disease, bullying or some other factor their color can be affected.
-Quality of the food they're being fed. Just like water parameters and health the better the food fed the better your parrot will look and feel.
There are color enhancers available on the market but I can't speak as to their effectiveness because I have no personal experience. Examples of such enhancers are NAN lighting which makes all reds/ oranges look more intense when lit by them. You could also try Red LED lights to the same end. Flowerhorn breeders and sellers also sell color enhancing food such as ALIFE, Ching Mix and Grand Sumo. Again I can't testify to how effective they are but from reading their ingredients I can't see them helping enhance color better then any other quality pellet food. They also use Power Pink to enhance reds and oranges in Flowerhorn and Parrot coloration. These products contain astaxanthin and other natural color enhancers found in shrimp and other natural foods that are believed to help enhance fish coloration.