Color−color diagrams of spectroscopically confirmed quasars (red) and stars (blue) in RCS-2. The upper diagrams show the optical g−r vs. r−i (left) and r−i vs. i−z (right) color plots. The bottom plot shows the NUV-g vs. g−i color space when including GALEX data. It can be seen that including the UV data provides a clearer separation between quasars and stars compared to solely optical data.