Personally, I think it still matters b/c you see the substrate below the plants if your substrate is deep. But I think the color of play sand is awesome in planted tanks. If you look at photos of tanks, lots of people use light colored sand. Keep in mind, however, that play sand is quite fine, which can lead to anaerobic conditions (not good). You might consider getting some malaysian trumpet snails to "turn" the sand. You probably won't get rid of these once you have them though. Also remember that sand is inert (no nutrients), so you might want to use plant tablets in the sand. You sound like you don't really like the way play sand looks. It might just be easier to spend the extra money on a substrate you think looks better and that has more fertilizers in it for root feeders.