Colour-colour diagram with the AGN sample colour-coded by the average of the intrinsic X-ray luminosity (in the 0.2 − 2.3 keV band) per bin, following Liu et al. (2022b). The solid black line differentiates extragalactic objects on top from Galactic objects at the bottom according to Salvato et al. (2022). The coloured tracks indicate the colour-colour evolution with redshift of the SED templates from Salvato et al. (2022), with z = 0 shown as a circle. The purple track represents a spiral galaxy, brown represents a lenticular galaxy, orange represents an elliptical galaxy, red represents a Seyfert 2, and pink represents a quasar. The squares indicate the values of the redshift of z = 0.2,  0.4,  0.6,  1.0,  1.6,  2.0,  3.0. The black dashed line indicates the trend of the quasar SED when more reddening is applied.