i-z colour evolution. The colour range evolution of the model is tested against observations (coloured dots). The model range is shown in grey, for three configurations: the dotted curve is a fiducial model with fixed FeII template and emission line strength. There is good overlap, except near z=0.6, z=1.2 and z=1.5 at negative i-z colours. Increasing the emission line strength range creates an overlap at z=0.6 and z=1.5 (dashed curve). Additionally increasing the FeII template strength range (grey curve, full model range) also produces a good overlap at z=1.2. However, at z=0.8, some observed eFEDS colours are lower than the model.