Tempera paint. Make sure to use a stencil. It might bead a little. It will depend on the table cloth. Don't get water in the brush, or it will cause it to bead.
Dries fast, cleans up easily and is non-toxic. You can buy it at Wal-Mart or OfficeMax.
The first link is a brief history, the second is product info.
But if the paint isn't working, use stickers. You can go into the scrap booking/craft aisle and get funky shapes and colors along with polkadots. There are a lot of stickers that aren't ugly or fragile.