I saw this idea in a craft book. I wish I could site which book it was from but I truly don't know. Anyway, I've changed the idea up a bit but I tried to create bubble paint envelopes. first, I mixed dish soap, food coloring, and water in a small bowl.
next, you will also need some plain envelopes, and a straw. I also would suggest putting newspaper or towels on the counter because it is bit messy and food coloring is hard to get out. I also would wear clothing you don't care too much about.
you will lay the envelope down and then put the small bowl on top. you blow bubbles to over flow and land on the envelope. They will pop and
leave a colored bubble smudge on the envelope.
Once you have done it all over the envelope. I hung them to dry with clothespins.