Colour-magnitude diagrams with isochrone fits and Be star counts for the Small Magellanic Cloud cluster NGC 330 (left) and Large Magellanic Cloud cluster NGC 2164 (right). Hα emitters are marked in red. Bottom panels: Be fraction counted in bins as defined in the top panels. The errors are given by the binomial counting error. The bins have a gradient of 2.0 and 1.8 for NGC 330 and NGC 2164, respectively. Mass values associated with the bins are provided by the isochrone fit. For both clusters, the isochrone depicts stars with initial rotation equal to 0.6v_rot/v_crit. For NGC 330, the isochrone age is 30 Myr, the distance modulus μ = 18.8 mag, and the reddening is E(B–V) = 0.1 mag. For NGC 2164, the age is 80 Myr, μ = 18.3 mag, and E(B–V) = 0.12 mag. Data are from Milone et al. (2018).