Posterior fitting to obtain the best value of R_V. First panel: optical CMD V − I versus I from Ortolani et al. (1995). Second panel: Gaia EDR3 G_BP − G_RP versus G CMD. Third panel: corrected NIR HST CMD. The cyan dotted lines are the isochrones considering the best fit from the standard isochrone fitting and standard extinction coefficient (R_V = 3.0). The embedded plots show the χ² function to the variation of R_V. The solid red lines are the isochrones with the best R_V value. Finally, the blue horizontal lines denote the isochrone HB and turn-off mean locus.