Colour-colour diagram to separate galaxies from type 1 AGN as in Euclid Collaboration (2024a). Filled contours show the distribution of type 1 AGN from the lightcone here presented, separated into those dominated by the AGN component (f_AGN > 0.5, orange contours) or the galaxy component (f_AGN < 0.5, blue contours). The distribution of spectroscopically confirmed type 1 AGN from the Chandra-COSMOS catalogue Marchesi et al. (2016a) is shown with non-filled red contours. In all cases, the samples have been cut at z < 3. The contour levels represent iso-density lines, corresponding to the 50th, 75th, 90th, and 99th percentiles of the distribution. The grey line shows the best selection criteria found in Euclid Collaboration (2024a) to separate type 1 AGN from galaxies and type 2 AGN.