The structure of the interface between water and self-assembled organic monolayers having different roughness and polarity is investigated by molecular dynamics computer simulations. The electronic absorption spectrum of an adsorbed chromophore at these different interfaces is computed and correlated with the structure of the interface. Several different electronic transitions characterized by different changes in the electric dipole moment are considered. We find that the effective polarity of the interface is greater than that of bulk water in contrast to the situation at several liquid/liquid interfaces, but in agreement with recent experiments at the liquid/solid interface. We show that this higher effective polarity is due to a contribution from the polar groups at the surface that is larger than the loss due to the decreased interaction with water.