0.27 \pm 0.01$ (see Table \[table:passivefraction\]). 7C has a similar red fraction to the $z=1.62$ protocluster ClG0218.3$-$0510, which has $f_{\rm red} = 0.48 \pm 0.15$. So the enhanced red fraction in 7C seems typical for mature protoclusters. The dense environment of the protoclusters appears to have a strong impact on the colours of their member galaxies.

Quiescent galaxy fraction {#sec:UVJ}
-------------------------

In low-redshift clusters the galaxies that lie on the red sequence are predominantly passively evolving, old galaxies. However, dusty star forming galaxies (with $A_V\sim1$-3) exhibit colours similar to those expected from quenched, passively evolving (i.e. quiescent) galaxies, and these galaxies make up approximately half of the red infrared-selected galaxy population at higher redshifts [@Kriek2008]. Furthermore, recent literature has also shown that high-redshift clusters and protoclusters do contain dusty star-forming galaxies [e.g. @Brodwin2013; @Dannerbauer2014; @Smail2014; @Santos2015]. The enhanced red fraction of sources in 7C could therefore be ascribed to an excess of dusty star-forming galaxies and/or quenched, passively evolving galaxies. Here we use the rest-frame $U,B,J$ colours (observed $i',J,[3.6]$) to separate these two populations.

Using the method outlined in @Williams2009a, @Papovich2012 used the observed-frame $z'$, $J$ and 3.6bands (rest-frame $U,B,J$) to separate galaxies in the $z=1.62$ cluster ClG0218.3$-$0510 into quiescent 