Baeyer has suggested that the nine carbon atom system of xanthone may act as a chromophore.
In other words, an auxochrome in addition to the chromophore group transforms a colorless chromogen into a colored one.
This is in agreement with the chromophore ideas of Hugo Kaufmann.
chromophore chro·mo·phore (krō'mə-fôr') or chro·mat·o·phore (krō-māt'ə-)
A chemical group capable of selective light absorption resulting in coloration of certain organic compounds. Also called color radical.