Theoretical evolutionary tracks, represented in the T_eff vs. M_bol plane. The colour of the tracks indicates their metallicity: black for solar metallicity, magenta for LMC typical metallicity, green for SMC typical metallicity. The coloured points along the tracks are separated by 0.1 Ma, and their colours indicate mass-loss. Left a): Geneva models, from Ekström et al. (2012), Georgy et al. (2013). No tracks for LMC metallicty are available. Solar metallicity is Z = 0.014. The tracks shown here correspond, from bottom to top, to stars of 12, 15, 20, 25, and 32 M_⊙. Right b): models from Brott et al. (2011). The evolutionary tracks shown here are, from bottom to top, those of stars with 12, 15, 20, 25, 30, and 35 M_⊙.