Play sand isn't really suitable for aquarium use, it would be better to use pool filter sand. Larger, more uniform grain size and it won't pack down tightly like play sand will. If you have fish that root, play sand can quickly become a nightmare as well due to smaller particulate staying in the water column and potentially entering your filter. Bad news if that happens!
Certain kitty litters are acceptable for substrate use as they are clay based. Many kitty litters have a gray color. Others who know of an acceptable brand for this can chime in.