Yellow labs you'd have to stay with mbuna but don't worry there is a large amount of them with vastly varying colors and paterns, the only other options to keep them with are synodontis species or clown loaches, actually some haps may work with them but not the demasoni
Pseudotropheus, and other labidochromis are good choice, cdo you have hard acidic water? that's what you need for thwm there easy to breed if your intrested in that but not like guppies, are extremely active colorful and intelligent