Two-colour diagrams showing photometry results of star clusters from this study. Panels a–c show T aperture photometry; panels d–f give the C aperture photometry. The grey colour in the background indicates areas occupied by stochastic star cluster models with masses from 10² to 10⁵ M_⊙. Colour indices indicated on the X axis are constructed from T magnitudes in panels a–c and from C magnitudes in panels d–f. The subscript TC indicates that colour indices are based on T and C aperture photometry in panels a–c and d–f, respectively. Arrows indicate the extinction vectors of A_V = 1, assuming the standard Milky Way extinction law.