Definition of Chromophore
A chromophore is a group of electrons and atoms that is responsible for imparting color to an organic molecule. This concept was first explained in 1870 that there is a relation between the structural properties of organic compounds and the color they have. It was noted that the aromatic and nitro compounds like quinone impart colors and these colors vanish the moment the compounds undergo the process of hydrogenation.
The unsaturation of a compound is due to the presence of electrons that are not restricted in covalent bonds but are occupying larger regions of space. These electrons hence are able to absorb light energy and transmit the remaining light which is, therefore, the color of the compound that is observed.