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 upright in a beaker of water then all the colours will separate.

Depending on chemical properties of the components of the ink, some colors may travel further up the paper and some inks may separate so that individual components can be seen.