This is usually a close to end of year project. The students get excited when I tell them we are going to make a butterfly with paint, but we are not going to use brushes and our fingers will not touch the paint! We review the primary colors and I demonstrate how they will fold the paper - "short side to short side". We open the paper up and I squirt some of the primary colors in lines an drips on one side in the shape of a V.
I refold the paper and show the students how to gently rub in circles on the folded paper. They will feel the paint be squished around. I used to use say "wax on - wax off" with the students...but only the occasional aide in the classroom knows what I mean these days!
After rubbing the paper the student is excited when I tell them to open it up and see what you got. The Oooo's and Ahh's that always follow bring smiles.
While I do this with a couple of students at a time at a table, the students work on making a butterfly body on black paper using construction paper crayons.
Here's my example -
The next class we will cut out the dried paint wings and glue the body onto it.
I do a similar project with my 1st graders. We do the same process only with one color + black on bottom and white on the top to help teach value tints and shades. Instead of a butterfly they make a longer body to create a dragonfly.