Colour diagnostic plot. The GRAHSP templates (coloured dots as a function of redshift) cover the entire plane. The observations are illustrated by coloured contours containing 99% of each sample. At the centre-left, quasars dominate (red outline, DR16QWX), while the eFEDS sample includes a wider distribution. The dashed diagonal line demarks the separation of Salvato et al. (2022) between galaxies (above) and stars (below the line).