Upper panels: color–color Hess diagrams for the sample of sources with ugri photometry, over the color interval expected for GCs and UCDs. The dark-blue lines show the linear spaced contour levels of sources in the master GC catalog. Filled squares show the integrated colors from the SPoT stellar population synthesis code. White, light-gray, black, and dark-gray symbols indicate metallicity [Fe/H] = [−1.3, −0.7, 0.0, 0.4], respectively; symbols size scales with increasing model age, ranging between 4 and 14 Gyr, with 2 Gyr step. Same metallicity models are connected with dashed lines. Left color-color panel: we also draw with dotted lines the color intervals of GCs assuming ±3 − rms_MAD with respect to the median values in Table 7. Middle and lower panels: (g − i) and (u − r) color histograms, respectively, for the master spectroscopic (left panel, green histogram), photometric (middle, yellow), and combined (right, blue) GC catalogs. In the third histograms the data of UCDs are also shown (orange), expanded by a factor of five for sake of clarity. Only sources brighter than m_g = 23.5 mag are considered.