Some kids used only one color.
Some kids used many colors to make patterns.
Some kids used many colors and layered they paper with so much paint it made the neatest textured painting.
Some kids used the sponges on the skinny side and others used the fat side.
I have found that painting with the strangest things make the neatest looking product and provide the best process oriented artwork.
If you want to learn more about process versus product artwork, you can visit this previous post.