Stellar evolutionary models of Bruzual & Charlot (2003) are calculated to four different metallicities, for the range of stellar ages of 1−20 Gyr. The models use their “Padova 1994” evolutionary tracks, the Chabrier (2003) Initial Mass Function (IMF), and STELIB spectral library (Le Borgne et al. 2003). The tracks are calculated for the same color indices as the observations shown in Fig. 6, and the black symbols represent the same galaxy samples as before. The ranges spanned by our observations are marked with the hatched regions.