Have a go at making your own rainbow salt tray. Toddlers and preschoolers will have lots of fun watching the colours come through when they draw pictures, create patterns and write their name in the salt. It is cheap to set up and you will already have the items at home.
Kids will have fun making their own garden fairies, especially over summer when plants are in full bloom. Teach them the names of the flowers that you use, discuss the different shades of colour and how plants grow.