Relationship between the stellar mass-to-i-band luminosity ratio and the g − i colour index, as predicted by the calibration of Zibetti et al. (2009) (green solid line), and our models of galaxy evolution for unperturbed galaxies of different rotational velocity and fixed spin parameter (λ = 0.05; red open symbols), as well as for galaxies undergoing a ram pressure stripping event (blue symbols).