Equivalent width of Hα as a function of the stellar mass of the galaxy. Left panel: we used Eq. (2) to distinguish between red and blue galaxies. Right panel: we relied on the classification performed with a machine-learning code trained with strong EL and weak EL galaxies. Strong ELs were defined as those with EWs greater than 3 Å in any of the following emission lines: Hα, Hβ, [O III], or [N II], and weak ELs are all others. The dashed horizontal lines mark the 3 Å limit in the EW(Hα). Density contours are drawn in black at the top.