For this project I used about 1:1 ratio of washable tempera paint diluted with water. And also experimented with water + food coloring. Both worked great. If you choose to use the food coloring, make sure to paint in a place where stains don't matter.
Cover your diluted paint with foil, poke nifty toothpicks into each compartment and freeze. I froze a couple of "just water" to play with on the patio.
You can use either a fancy-schmancy ice cube tray or plain Jane. You'll have better results if you fill'er up. You don't want a skimpy paint cube to melt off your toothpick. No big deal if you're skimpy - just means you'll eventually paint with your paws instead of the pick.
Below you'll see where I didn't mix the green very well and the paint settled to the bottom. It didn't affect the performance. She still painted with a happy heart.
Look - they're all friends, playing so well together. Wanna know why Mr. Blue is so blue? I broke him when trying to dislodge him from his frozen home. Mr. Purple is such a good friend to console and embrace Mr. Blue, doncha think?
You know it's a great project when Mr. Intensity sticks out his tongue.
The food coloring and water painted like... a lot like...well, water... colors. Some friends joined us - they had a blast together. This paint project is perfect for all ages.