Distribution of the candidate WD sample (after the astrometric fidelity cut) in the (B − G) vs. (G − R) color–color plane. The density distribution shows a sharp ridge where our objects of interest are located, objects with SEDs (or colors) of single WDs. The left panel shows the full color distribution, which exhibits a subset with an enormous spread in colors: most are presumably binaries, involving a WD (possibly with an accretion disk) and a low-mass star. The color cut, shown in the right panel as the blue line, eliminates most of those, while preserving ≥95% of spectroscopically confirmed WDs. This is an example of a sample selection cut that leaves the selection function for the objects of interest essentially unaffected. It simply makes the sample purer, lessening the need to explicitly model contamination.