Colour-colour diagram of the sources with reliable redshifts (NORMQ = 3), colour-coded by their class as in Table 3. For the colours g − r and z − W1, g, r, and z come from the Legacy Survey, while W1 comes from WISE. Orange squares represent broad emission line objects (QSO), while pink diamonds show the objects that have a broad line with an absorption feature (QSO_BAL). Green triangles indicate extragalactic objects with narrow lines (GALAXY), and purple stars represent Galactic objects (STAR). The blue triangles represent BLAZARS, although these sources do not have reliable redshifts. Yellow circles indicate Other Galactic objects (z < 0.001) that have a reliable counterpart, though they were not observed with SDSS. Both BLAZARS and Other Galactic objects do not have NORMQ = 3. The black line divides objects between extragalactic (above) and Galactic (below) as in Salvato et al. (2022). Histograms on the top and right show the distribution of each photometric colour per class.