The Lumina color changing phenomenon is a reaction to the mildy toxic oil, gelatinous goo and oily secretions which Turpentines, Waterhorses and Albinos are respectively covered with. The Luminas remove their scales in order to get rid of the oil or goo, so their color changes to reflect their scaleless body as per their official description: "... if one of their scales has so much as a scratch or a defect, they'll remove it. Luckily, their scales grow back quickly, and each new growth is more beautiful than the last." Bred eggs of a Lumina x Turpentine/Waterhorse/Albino couple are not affected by this and hatch as ordinary Luminas.