SDSS \((u-r)\) colors of the RGZ hosts are consistent with expectations for giant elliptical galaxies. The majority of the \(\sim3200\) galaxies lie along the red sequence, with a small amount of scatter at higher redshifts. Earlier results showing them all over the map were likely due to a combination of galaxies near the telescope observable limit and/or \(u\)-band dropouts.
The small fraction of RGZ hosts in the blue cloud are interesting and potentially worthy of individual follow-up; they might either be genuine spirals or blue ellipticals with recent amounts of star formation, possibly merger induced.