Left: X-ray–to–optical flux ratio f_XO vs. the optical to infrared colour i–IR (symbols are the same as in Fig. 6, but with the addition of the of mid-IR selected AGN candidates as in Fig. 10). Right: optical to infrared colour i–IR as a function of redshift for AGN1 (red), AGN2 (blue), and galaxies (magenta). SED models for QSO1, QSO2, Sy1, and Sy2 from the photometric redshift fits are overplotted (see legend).