Get yourself a wee bit of dish soap.
And God's gift to ears.
A dish full of whole milk. Don't use skim or 2% - it won't work.
Don't forget the excited 12 year old.
So here's what you do. Pour the milk and wait for it to settle. Drop a few drops of food coloring into the milk. Take your q-tip and dip it into the dish soap. Dunk the soapy q-tip straight into drops of food coloring, and watch the magic!
Photo's really don't do it justice. You're going to have to try this one out yourself.
I tried dipping the blank cards into the milk to capture some of the colors and patterns that came out. Some turned out better than others, and the colors are much more muted when dried, but hey, it was worth a shot.