if it is an ocellaris then it will lose the big spots and keep the one in the tail, if ti is a temensis it fades but gains shiny spots, if it is a monocollus the spots will be strong...
i'm no expert in cichlas, but i think this is it...
Many of my pbass have done this often...they are very variable with pattern fade and intensity....by seeing your pic I knew exactly what you were refering to...sometimes they will almost turn a green color where normally black and sometimes almost pattern fade to white....havent pinpointed a cause of this mood alter but I can tell you it is no big thing....mine did it alot when growing up and all are just fine...water params in check and temp in check...no stress ect.. they would do it out of the blue and then turn back normal....this went on for a period of approx 2-3 months then they stopped doing it around 9-10"