Synthetic colour–magnitude diagram of a 35 Myr star cluster at SMC metallicity, where each dot represents one single star and the colour gives the critical velocity fraction, v_rot/v_crit as indicated by the colour bar. Gravity darkening is included assuming a random orientation of the rotation axis. Over plotted are observations of SMC cluster NGC 330 (Milone et al. 2018), with Hα emitters marked by orange squares and normal stars as orange star symbols. Right panel: region indicated by the red box in the left panel. To convert the models to apparent magnitudes a distance modulus of 18.92 mag and a reddening of 0.06 mag were used.