This is a fun and quick idea for children (and adults!) of all ages. You need:
A tray or dish
Food colouring or liquid water colours* (these give a brighter colour)
Squirt some shaving foam into the dish and smear around a bit. Add some drops of your favourite colours. Use the lolly stick (or fingers) to whizz the colours around in swirly patterns. Place a sheet of paper on top and press down. Remove the paper and use the side of the lolly stick to scrape off the excess foam. Underneath you will find a beautiful and completely unique marbled pattern!
*You can by liquid water colours on amazon. They are not cheap but a little goes a long way!