http://www.cichlid-forum.com/articles/m_estherae.php
(Maylandia [Metriaclima deprecated] estherae)

snipped directly from the article:
At about 2.25 inches males will start to put on a light blue shade all
over their body and fins, and thus become somewhat unworthy of their name.
The females just put on a brighter orange color as they mature.

hth

/Tommi

Feed your fish three times a day and do water changes every other day. See
if they have color yet at 2.25 inches. Or, feed them once every other day
and you'll find they color up at a much smaller size. Size is relative.
Tim