Comparison of ABC sources (blue circles) and Roma-BZCAT sources (red circles) in the SDSS g − r versus u − g (left panel), r − i versus g − r (central panel), and i − z versus r − i (right panel) color–color diagrams. Gray points in the background represent random SDSS sources and the black continuous lines indicate KDE isodensity curves containing 60%, 70%, 80%, and 90% of the random sources. On the top and on the right of each main panel: we show the normalized distributions of the SDSS colors for the ABC, Roma-BZCAT, and random sources. The ellipses in the panels indicate the average uncertainties on the SDSS colors.