IMO black sand makes their colour too dark making them difficult to spot, light sand would be a nicer to the eye choice but is more difficult to keep looking clean. Fine light gravel would be a better choice
It's amazing how easy maintenance is. If done regularly and thoroughly
I'd go with the natural color sand rather than black or white but that is personal choice. I'used black substrtes in heavily planted tanks w/Neon or other fish with strong prismatic colors and it looks great, but with most pigment colors it does cause the fish to darken more than I like. Darkening to reduce contrast with the substrate can be a survival trait in the wild. FW fish with strong prismatic colors tend to be from peaty waters where such coloring aids the schools in keeping individuals in sight in tannin-stained water.