HRD of the PoWR^HD WN4b models (red squares), with the effective temperatures at the critical radius T_crit (top panel). The GENEC evolutionary tracks without initial rotation from Ekström et al. (2012) with M_ini = 40, 60, 85, and 120 M_⊙ are shown, where we display effective temperatures not corrected for the wind. Separate segments of the evolutionary tracks are colour-coded by surface abundance: bold yellow denotes WNh stars (0.4 > X_H > 0.02); bold black denotes WN stars (X_H < 0.02); bold magenta denotes WN/WC stars (X_C > 0.02); and bold blue denotes WC or WO stars (X_C > 0.2). The tracks are further indicated in bold grey according to the criterion τ(R_*) > 1.45 from Aguilera-Dena et al. (2022) (see also Eq. (4)). For comparison, the PoWR^HD models of M31WR99-1 and WR2 from S25 are shown as well. The bottom panel shows the same PoWR^HD models, but now comparing the wind-corrected temperatures given by GENEC with the determined T_2/3 temperatures at τ = 2/3. In both panels the H-ZAMS from Ekström et al. (2012) and the He-ZAMS from Langer (1989) are shown as the grey and green dashed lines, respectively.