Re: Why do some fruit flies have sepia eyes and how do they get them?

The most common way for a fly to get sepia coloured eyes is through a mutation
in the "sepia" gene. 

Flybase entry for
sepia

This is a gene that creates an eye pigment, when mutant, the eyes are not the
normal red but slightly brownish. 

You can find information about this, and other Drosophila mutations, at
flybase.org. 

Cheers,

Sanjida