Gaia DR3 G_mag corrected for distance against G_BP − G_RP for the selected sample, color-coded with the LC. The solid black line shows the ZAMS. The evolutionary tracks for 9, 15, 20, and 40 M_⊙ up to the end of the He-burning phase obtained from MESA without initial rotation or extinction are shown in gray. No reddening is applied. Instead, a reddening vector with Δ(A_v) = 1 is indicated with the red arrow. Two diagonal dashed black lines show two extinction lines for a 20 M_⊙ star and for the approximate position in Fig. 5 in which the same track crosses the value of log(ℒ/ℒ_⊙) ≈ 3.5 dex, respectively.