(u − g) vs. (g − z) color–color diagram of our local galaxy sample computed from pixels with signal-to-noise higher than 3 (pixp3; left panel) and higher than −5 (i.e., total colors, labeled as pixm5; right panel) in the Hα detection images. The colored contours show the density of sources to highlight the presence of local maxima. The dotted lines in the left panel mark our selection for the Red sample (red area), the Blue sample being the complementary set (blue area). The upper- and right-side normalized histograms are the density projections in (g − z) and (u − g), respectively. The red and blue shaded histograms in both panels mark the Red and Blue samples selected with pixp3 colors.