In planning for a VBS activity, I discovered something neat ...
KoolAid will dye sand and salt ... which makes for a very inexpensive version of sand art! Just one packet of KoolAid will die several cups of sand (I used "play sand" from Walmart). You can use more or less KoolAid in order to get the color you want. Just beware of using it with littler kids b/c it makes the sand smell really good!
If you buy that pre-dyed sand art stuff it's over $6 for 3 pounds at Walmart. I thought that was outrageous. So I looked for an alternative and for about $4 I had more than enough (plus LOTS of left overs) for 20 kids to fill baby food jars with colored sand. And I still have 3/4 of a bag of sand left!
-Beth