Best selection (type B) criterion for all AGN in the EWS using Euclid and Rubin/LSST filters (shaded rey area). The shaded red areas correspond to the colour distribution of all AGN, while the blue lines are the contour levels of the remaining galaxies. Levels correspond to 68%, 95%, and 99.7% of the distribution. We also present example SED tracks for one AGN1 (yellow crosses), for one AGN2 (green squares), and one spiral galaxy (cyan circles) from z = 0 to z = 6, with steps of Δz = 1. As an indication of how strict the best selection is, the hatched green area limited by the two dashed green lines show the extent of all the best selection criteria derived with the bootstrap approach. The dotted black line and the dash-dotted black line correspond to the best selection with P > 0.9 and C > 0.9, respectively.