Color changing cichlid

I've had a Pseudotropheus auratus (I've also seen the name as
Melanochromis auratus) cichlid for around 2 years. It has been with a
pleco and some orange 1 inch cichlid I have never identified somce it
was introduced. I have also had 3 tin-foil barbs in with them for
about a year. They are all in a 29 gal. tank that has great water
quality, proper filtration, and a constant temperature of between 78
to 82 degrees.

I have heard of cichlids sex changing, but there is no reason for this
one to. When I bought it it was of the female coloration (Yellow with
black horizontal stripes). It has since changed to the male coloration
(Black with dark-yellow horizontal stripes), back to the female
coloration, and once again to the male colors.

What could be going on with this cichlid. I would appreciate any input
you may have.

Thank you