I built the bar top for my moms tiki bar when I lived home about five or six years ago. She had the colored sand. I would presume from a craft store? It was all neon colored.
I used dap wellwood to glue down the caps, then poured sand, leveled with a plastic spreader, then poured resin. The resin application is fun. You get to blow torch it to get it to thin and let all the bubbles out. The one gallon kit from us composites would be plenty for your project.
As always, do the resin work outside or in the garage and you have to build a dam of some sort all around the outside to keep it from just running away.
I'll snap a pic of the corn hole boards and it should explain more. I also asked my mom to search for pictures of the old tiki bar top. I'll post them up when she gets them to me.