Some Mbuna have colorful females. Females of haps and peacocks are drab. This is why you go with an all=male tank. Well some do, I prefer mixed gender groups even with haps and peacocks.
If you want colorful females and mixed gender groups then think in terms of 4 species with 1m:4f of each in a 90G. Avoid the most aggressive mbuna like auratus, kenyi, johannii, etc.
What is your one must have Lake Malawi fish? We can suggest other species that would do well together.