Healthy, good quality rivulatus have plenty of color, especially as they mature, and it doesn't require a special substrate to bring it out ime, so there's room for some personal preference. Mine is dark background, light sand, and easy on the overhead lighting (not too bright). Substrate isn't the only factor, water quality, food, and lighting are just as important. In fact, it's surprising how the right bulb can enhance your whole tank, adding clarity and vibrancy to the natural colors of plants, fish, sand, etc., while some bulbs can muddy up colors by comparison. You can better see this when you can compare them side by side. (Not talking about extra blue bulbs, like actinic, etc., but getting the right natural bulb.)