F555W vs. F336W − F814 CMD for all the selected stars of the cluster (see text), corrected for the effective magnitude zero points for each band, a true distance modulus of (m − M)₀ = 18.43 mag, and a foreground extinction of A_V = 0.28 mag (Goudfrooij et al. 2018). The black arrow indicates a reddening vector corresponding to A_V = 0.1 mag for reference. The grey shaded region indicates the Cepheids instability strip. The luminosity and effective temperature of the strip are taken from Marconi et al. (2004) and are coloured with the new YBC bolometric database available at http://stev.oapd.inaf.it/YBC/ (Chen et al. 2019). The diagram clearly shows the MS split and the extended MS turn-off. The inset shows a zoom of the MS in which the two MSs are selected and coloured to indicate the bMS (in blue) and the rMS (in red; Milone et al. 2017).