M$_{\mathrm{B}}$ is constant with local density.

Several observations of individual clusters at $z$$\sim$1.5 find that they already have a significant passive galaxy population (e.g. McCarthy et al. 2007; Kurk et al. 2009; Wilson et al. 2009; Strazzullo et al. 2010), indicating that at least the color-density relation extends beyond $z$$\sim$1. Further, using an early release of the UKIDSS Ultra-Deep Survey, Chuter et al. (2011) find a strong relationship between rest-frame (U $-$ B) color and galaxy environment to $z$$\sim$1.5, with red galaxies residing in significantly denser environments than blue galaxies on scales below 1 Mpc. Using a more complete UKIDSS Ultra-Deep Survey data release, Quadri et al. (2012; Q12) use a mass-selected sample to show that galaxies with quenched SF tend to reside in dense environments out to as least $z$$\sim$1.8. Specifically, they find that the quiescent fraction increases with local density, even at high redshift.

It is difficult to synthesize these observational results into a single coherent picture, as they use different wavelengths to measure color and/or SFR, use different methods to measure local density, observe different fields and define their galaxy samples differently. In addition, semi-analytic models (SAMs) have not reproduced observations of the reversal of the SFR-density 