Age versus colour. The solid lines represent the models by Marigo et al. (2008) and the vertical dashed lines are the colours by Prugniel & Heraudeau (1998) using a 30′′ aperture. On the right the M/L_R values for a given age (Chabrier 2003 IMF – using M_⊙ = + 4.42) are shown. The (B − R) colour is not really age discriminative, however, an age of ~8 Gyr and M/L_R ~ 4 is consistent with all other colours (cf. an age of ~ 4 ± 1 Gyr by Li et al. 2007, based on [B − V] and [B − K] colours and the models by Bruzual & Charlot 2003). Note that a M/L_R of 3.1 is well described by our dynamics, but 2.8 is still possible (Table 3). A M/L_R as small as ~2, to accommodate the age estimate by Li et al. (2007), does not match our dynamics.