Comparison of color–metallicity relations with theoretical isochrones of different age (top row) and different α-enhancement (middle row) and transformed (V − I) relations (bottom row). Left panels compare the relations at F814W = −3.5, right panels at F814W = −3.0. The (V − I) relations are taken from Saviane et al. (2000, S+00), Lee et al. (1993, L+93) and Da Costa & Armandroff (1990, DA90). The S+00 relations are given on two metallicity scales: the ZW scale (Zinn & West 1984) and the CG scale (Carretta & Gratton 1997). The gray contours show the 1σ, 2σ, and 3σ confidence levels of the fit. The two lines for the observational relations are due to differences between the observational and synthetic transformations from Sirianni et al. (2005).