- Take some cans of paint, a "recipient" (which will receive the new color(s)) and any number of "donors" (which will be added into the recipient can). The receipient must have sufficient empty room for adding the paint.
- Freeze the recipient.
- You need a tube to connect the recipient to each donor. You can buy special "mixing caps" made for this purpose, you can use a needle cap, or you can just use the straw inside of a cheap pen like a Bic.
- Remove the caps from both cans. Put the warm donor can on the ground and invert the cold can above it, and connect the tips via the pen tube. Warm paint will shoot into the cold can.
- Repeat with more donor colors if you want.
- When the frozen can thaws, shake and use.
Enjoy.