Wikijunior:Big Book of Fun Science Experiments/Chromatography of inks
Get some filter paper - use a coffee machine filter or ask your science teacher for some (say please, it isn't free) - water and pens. First you put pen marks on the filter paper then stand it up right in a beaker of water then all the colours will separate.
Solubility describes how easily things will dissolve in water or other liquids, called solvents. Normally, the longer you leave something in water, the more it will dissolve.
Some colours in the ink from the pens will dissolve more easily than others; as the water soaks up the paper, it carries the ink with it. The more easily one colour dissolves, the further it travels.