Comparison of the U versus (U − V) CMD from NTT photometry (Momany et al. 2004) before (panel a)) and after (panel b)) the correction for differential (but not for the absolute) reddening. The horizontal branch stars lie at U ~ 17. The Δ(U − V) distributions of RGB stars with respect to the fiducial (red dash-dotted line on the CMDs) are shown in panels c) and d) for the uncorrected CMD, and in panels g) and h) for the corrected one. For SGB stars we show the distributions of the ΔU magnitude relative to the fiducial shown in the CMDs for the uncorrected (panels e) and f)) and the corrected (panels i) and l)) CMDs.