Upper left panel: color–color diagram for the full catalog of matched sources in NGC 3115 (gray dots) and catalog of GC candidates obtained using the photometric and structural selection criteria shown in Figs. 1–2 (orange circles). Green and blue circles show the GCs and UCDs from the literature, as in previous figures. Even with no color selection, the sequence of orange dots concentrates on the well-defined sequence of compact sources (stars and GCs). Upper right panel: as left, but color selected GC candidates are shown with pale-blue circles. SSP SPoT models for ages between 2 and 14 Gyr and [Fe∕H] between −2.3 and +0.3 are plotted with solid lines in various purple shades. Lower left: as in upper left panel, but for NGC 1399. In contrast to the UCDs candidates in NGC 3115, the (spectroscopically confirmed) UCDs in Fornax are all well lined up with the color–color sequence of GCs. Lower right: as upper right, but for NGC 1399.