I tried this project with a two year old today...BIG hit. We taped it to the floor first, but then used masking tape to tape it to a window. He really enjoyed the effect of painting with the light showing through. We used Q-tips or fingers for drawing utensils. I recommend this project as an alternative to finger painting because 1) it's less messy and 2) most toddlers I've worked with do not like the feeling of getting paint on their fingers.
Cool science experiment for kids! Rainbow Roses Get white or cream colored long stem roses. (Carnations work well too). Cut the stem according to the picture, you will then place 4 glasses of food color dyed water together. Put one piece of stem per color and allow the flower to soak up different colors.