Two-colour diagrams showing star clusters from Paper I and this study over-plotted on the distributions of models. The models of clusters (areas of grey colour) are with masses from 10² to 10⁵ M_⊙. The subscript TC indicates that colour index is based on T and C aperture photometry in panels a and b, respectively. Arrows indicate extinction vectors of A_V = 1, assuming the standard Milky Way extinction law.