Left: m_F814W as a function of the colour difference (m_F606W – m_F160W)-0.55(m_F606W – m_F814W) for the stars plotted in Fig. 1. Right: zoomed-in view of the pseudo-CMD plotted in the left panel around the MS region used to derive the ChM. The solid coloured lines, which partially overlap with each other, are the fiducial lines of the five populations identified in the ChM of Fig. 1. The fiducials of the corresponding sequences of equal-luminosity binaries are represented with dotted lines.