Evolutionary tracks of stars at solar (top) and sub-solar metallicity (bottom) showing their luminosity, L as a function of effective temperature, T_eff. Lines of constant radius are provided for reference. We highlight the evolution after core helium depletion in color, where the color refers to the initial mass. Yellow star symbols indicate core carbon exhaustion, and white star symbols denote the final time step calculated for models that did not reach core carbon exhaustion. The white circles in the lower panel indicate when the radius reaches a first maximum after core helium depletion. Above each panel, we indicate approximate ranges of effective temperatures typical for Wolf Rayet stars (WR), blue, yellow, and red supergiants (BSG, YSG and RSG respectively). The horizontal color scale above each panel indicates, for each effective temperature, the color as perceived by the human eye.