t.oliphant was close...but its Metriaclima lombardoi, not pseudotropheus. If its a male, it will gradually change colour from the blue to a golden yellow, or stay blue if its a female. They're nasty little buggers though, what are you housing it with?
Is your fish starting to show signs of getting some yellow colouring on the body? This is the Met. lombardoi. Female will stay this colour and the male will become yellow.
Had some, lost them when my tank broke, and found them to be not as bad as some people make them out to be. Thanks for the pic.