What you'll need:
Bowl of water
Paper towels, cut into strips
Three or more coloured markers, including black
What to do:
Draw a wavy line an inch above the bottom of each towel strip, using a different coloured pen on each.
Dip each strip into the water so that the bottom edge of the paper towel is submerged, but not the line of ink.
Hold in place as the water creeps up the towel. The ink marks will spread, revealing the different dyes that make up each colour.
Most colours are actually made up of several different dyes. As the paper towel draws the water out of the bowl, the water molecules bond with the different ink molecules and spread them.
The process of separating these dyes is known as chromatography. Grab a black marker and discover the several blue and red smears that it can make!