I prefer odd colorations over particular species, for example a red and green indo lord can be pretty boring while some of the brighter, more oddly colored morphs can be really mind-blowing (ie: pink & green with purple centers, bright pink etc.)
For color variability I'd agree that micros come in the widest range of colors. They are really bright also so they stand out in a tank.
For a species that has consistent coloration I like metallic green froggie walls and dendros =)