Not really true, the difference is there is multiple closley related fish in close areas that are diverse in solid colours. (Mbuna)
So in a small place you can have a yellow fish, blue etc.
Also you can pack your tank with different coloured Malawi Cichlids with no real worrys.
If you could pack a tank with Gold Saum's, Gold, Red Spotted + Rotkeil Severum, Midas, Vieja Argentea, Peacock Bass, EBJD, GBR, Salvini, Elioti, HRP, etc and none growing over 4" .... I think that tank would be much more impressive colour wise.