Make colored sand art by stirring a chalk stick in a bowl of salt. it changes the color. Stir less for light color and more for dark richer color. (I used to do this with salt and food coloring. but the chalk stick idea is brilliant!
A water balloon with a glow stick on the inside, in a stocking, hung from trees, patio cover, or the ceiling. Same pin elsewhere said: "Put a glow ball in a white stocking and hang many from trees or the ceiling." But what are glow balls?