The coloration of the Orange Mossambica comes from two very distinctly different sources. The orange is somatic and occurs as pigmentation throughout the dermal layer.
While breeding for it appears to bring out more and more orange, it appears it is the reduction of black chromoatophores that actually allows more of the orange to become more apparent.
Those areas of the fish that respond to hormones, such as the front of the head and the tip of the spines show the most darkening when sexual stimulation or dominance is present. Therefore brooding females will show a darkening in these areas.
This Darkening of the chromotophores in response to sexual stimulation results in a fierce appearance as she defends her territory.
The colored tilapia, like the black tilapia are able to move the coloration chemicals into their chromatophores in response to their enviroment. Colored tilapia will appear much lighter if housed in a white container and so forth.
Much of the work I have done in my research was to select from those orange fish that displayed the most even coloration and breed for that characteristic.