This is a cool visual experiment you can do to show how the colouring from confectionery diffuses in warm water. Instructions are below.

Step 1

Take some Skittles (or other similar confectionery) and arrange them in a pattern around the edge of a small plate...
http://i.imgur.com/4XWRIBL.jpg

Step 2

Fill a jug with water from the hot water tap...
http://i.imgur.com/uKU5LQk.jpg

Step 3

Pour the water carefully into the middle of the plate, being careful to not pour too fast or you may disturb the position of the Skittles. You should keep pouring until the Skittles are roughly half submerged in the water...
http://i.imgur.com/H4vNM9p.jpg

Step 4

Wait for the magic to happen...
http://i.imgur.com/zSoUaUh.jpg

http://i.imgur.com/t6fih9u.jpg

Continue to experiment

Try different arrangements of Skittles and see how the created patterns change...
http://i.imgur.com/OZjFKK0.jpg
...and try different water temperatures to see how this affects the speed of diffusion.