Favorite No Cook Play Dough

This would be a sweet birthday gift - small batches of various colors of home-made play dough. My approach to play dough is very imprecise, but I roughly use this recipe from theimaginationtree.com. I like it because it requires no stove time.

1 cup plain flour
1 tablespoon vegetable oil
1/4 cup salt
1 tablespoon cream of tartar
up to 1/2 cup very hot water
food coloring

In separate bowls for each color, mix this ratio of dry ingredients, then add oil and color, slowly add water while stirring (if you get too much, just add more flour). Once it is starting to clump, kneed it with your hands. Of course there are a million variations you can add - scents, texture stuff like sand / oats / dry rice, or glitter. I guess a few drops of glycerine makes it shiny, but I've never tried that.