Colour–magnitude relation in the MS1054 cluster (top panel) and control field (bottom panel) line-of-sight directions. The solid line marks the colour-magnitude relation, whereas the dotted lines delimit the portion of plane that qualifies galaxies to be called red. The vertical line marks the considered limiting depth. In this figure, we use magnitudes in the Vega system, for comparison with the similar figures in Andreon (2006).