You may have heard of these wavelengths shortened to ROYGBIV, which stands for red, orange, yellow, green ... this experiment with isopropyl alcohol (rubbing alcohol) to see if the inks separate. So, ...

A pencil line is drawn, and spots of ink or plant dye are placed on it ... In the example below, red, blue and yellow are three pure substances. The sample on the left is a mixture of all three.

like this red ink. When the substance you want to separate is not soluble in water, like this permanent marker pen, you can use a different solvent, for example alcohol. For safety you may want to ...