Distribution of (W2 - W3) infrared colours for objects near the region identified as elliptical galaxies (W1 - W2) < 0.5.  Solid and dashed vertical lines show the  median colours of the all-sky and RGZ sources.  While sources randomly selected from the WISE all-sky sample peak near (W2 - W3) = 0, our current RGZ sample shows a large population with significantly redder colours - possibly from star-forming galaxies and/or ellipticals with enhanced dust.