A chromophore is the part of a molecule responsible for its color. The color arises when a molecule absorbs certain wavelengths of visible light and transmits or reflects others. The chromophore is a region in the molecule where the energy difference between two differentmolecular orbitals falls within the range of the visible spectrum. Visible light that hits the chromophore can thus be absorbed by exciting anelectron from its ground state into an excited state.
The video below explains about the biochemical background of chromophores, light absorption / reflection and the resulting colours that appear in nature.