Color-color diagram of our parent sample of ∼19 million galaxies. The plot displays where most galaxies in our selection are located. The green shaded area shows the density of galaxies from the parent LRG sample. The green solid lines shows the 1, 2, 3, and 6σ contours. The lens candidates and contaminants from this work are shown in overlay: Sure Lens (purple stars), Maybe Lens (open red triangles), and ring galaxies (open cyan circles). See Sect. 5.3 for details.