CMD of VVV-CL001. The green points represent stars retained after the re-decontamination process, while the orange points indicate the rejected stars. The red points correspond to CaT-confirmed members of VVV-CL001. The black cross marks the adopted fiducial point, and the blue curve shows the best-fitting theoretical isochrone. Inset: value of the metric M (Eq. (A.4)) for each tested combination of E(J − Ks) and ${\mu }_{K_s}$ (black points). The orange curve is the Gaussian fit to these points, used to identify the optimal values of E(J − Ks) and ${\mu }_{K_s}$ that minimize M.