Oxide paste (scroll down the page a bit to see the product info) from Vallejo. Fine texture, already has the color you're looking for, and should be more durable than PVA and sand, once cured. You can get a 30mL bottle to try out or a 200mL tub to base a whole army. If you don't have a local distributor, you can find it online at The Warstore or MiniatureMarket, as well as through various Ebay sellers and Amazon.
You
can find sand in various colors (including red) at craft stores, but it's tinted sand, not painted sand (i.e. translucent and satin instead of opaque and matte). Unpainted sand tends to look "off" or "out of scale" next to painted models. If you don't use the oxide paste, I wouldn't be concerned with the color of your sand or texture paste, as you'll be better off painting it, anyway.