yeah depends on the fish light colors will make there colors brighter so thats good for dark colored cichlids but cichlids with lighter colors can get washed out by white
darker substrate will bring out blues and reds but will darken lighter fish so it really depends on which cichlids and how you wan't them to look
i'd say that darker substrates make cichlids look better
Many darker and south american are going to be more vibrant on a dark substrate.Some africans will color up better on a white substrate.For example,I recently moved my lelupi from a tank with black sand cause they turned a muddy brown color.Now in a tank with white substrate theyre a hot orange color.