I finally found a answer ! Through reseach I discovered that we are not seeing things Yeah!.. here it is :
All fish can alter their colors to some extent, although most aren't cameleons some, like a couple of the flat fish have an uncanny ability to match their surroundings. Most others instead have what's known as a night/fright pattern, typically something that offers an additional amount of protection in the dark - like extra eye spots, etc. On the flip side, and in captivity it is not uncommon for a fish to fade its colors, many times due to nutritional defficiencies. What could happen in this case is a combination of factors - perhaps a response to environment such as the coraline algea, perhaps also a response to being fat and happy,as mine definitly is.
All in all nothing to worry about what-so-ever! Just enjoy it is the verdict!
Curiosity is the very basis of education and if you tell me that curiosity killed the cat, I say only the cat died nobly. - Arnold Edinborough