sticky board made with contact paper. Use string or construction paper pieces. a great idea would be to apply another sheet of contact paper to the sheet and hang it for art, especially if you used shapes or pieces of paper the kids colored themselves.
Investigation area. Enhanced with brightly coloured water (just using a small squirt of paint!), transparent pipettes, jars, tubes etc. encouraging the children to explore with colour mixing, and allowing them to watch the water travel through the various objects.