Pigments absorb certain wavelengths of light and reflect others.

Most photosynthetic pigments are not soluble in water and therefore can only be eluted using non-polar solvents.

Chlorophyll, for example, can be found in all photosynthesizing plants and algae. It absorbs light between 400-500 nm and 600-700 nm, depending on the structural groups attached to the porphyrin ring. As you can easily guess from its structure below, chlorophyll is hydrophobic.

A 3D model of the chemical structure of chlorophyll. A ring containing carbon, nitrogen, and hydrogen surrounds a single magnesium atom. A long hydrocarbon tail extends out from the ring.