Colour–colour diagram made for standard filters J, K, and N approximated here by rectangular boxes in Fig. A.4 showing the comparison of the vDC IMF and the MKDP IMF for different initial UCD masses, M_UCD. Since according to the ΛCDM cosmological model the upper limit to the age of the universe is t_max ≈ 13.7 Gyr, we plot only ages consistent with this constraint on a corresponding redshift (here values are plotted at a redshift of 0, 3, 6, and 9). The age evolution is shown by a colour scale that is the same for all plots.