Ashers store bought bath tub paint had ran out and not wanting to throw the bottles away I decided it would be a fun project to make our own. Plus side is that you know exactly whats going in it.
Food coloring (or you can make your own natural dyes using food. ie, beets, blueberries)
Use 1/3 cup soap for each dye batch.
Add cornstarch until it is the right consistency
Add food coloring
Fill old tub paint bottles or buy clear ketchup and mustard type containers and using your computer and plain address labels create your own "brand". You can title soaps after your kids names for extra fun.