Cut a paper plate in half to make the rainbow shape. Colour with your choice of colouring materials to make the rainbow. Then cut streamers into about 2 feet long lengths (or whatever you like), and glue on the bottom.
Add a ribbon to the top to hang – works well to hang on a curtain rod, or across the top of the window.
You can see the variety of rainbows that different-aged kids made – let your kids be creative and make them however they wish!