We love painting with corks because they make such fun polka dots and are perfect size for little hands. This was a fun exploration of rainbow colors and can be made to have a strict focus on order or you can have a more open ended view. Choose what works for your child. The goal for me was to talk about the colors and let her create. If you are looking for a way to teach the color order of a rainbow try this game we shared a few weeks ago.
Gather your materials. You will need some paper, scissors, corks, paint in rainbow colors, and a plate or tray to place them on. You may also want some painter’s tape to hold the paper in place.
Start by cutting the paper into an arc. We chatted a little about what other things are shaped like that. Headbands, earphones, and the door on her princess castle.
Next set up the cork in the different rainbow colors.
I arranged the tray in the middle of the arc for easy painting but do whatever is comfortable.
Paint.
My daughter grabbed the corks in order but painted them starting in the inner arc. Depending on your goal for this activity you could direct your child or students to start on the outer arc and make sure to stay within the correct order. This was not my goal. 
At three I want her to explore and play with the colors but most of all I want her to enjoy creating her own art.
I was so happy to see an easy and fun craft idea in my inbox this morning! My son and I did the craft after breakfast and he seemed to really enjoying the corks to paint with.
This is exactly the type of comment I love to see! Glad it was fun.
Going to try this after nap! Love that we already have all the supplies! Quick and easy! Thank you!!!!
WHAT A GREAT CONCEPT.LOVE IT.