Histograms of the rest-frame U − B colour (top panels) and diagrams of U − B vs. B-band absolute magnitude (lower panels) shown for DEEP2 galaxies in two successive redshift intervals: 0.75 < z < 1 (left-hand panels) and 1 < z < 1.4 (right-hand panels). The dashed line in the lower panels is the luminosity-dependent colour divider employed by van Dokkum (2008), which is used in this work to classify our galaxies into red and blue populations. Magnitudes plotted in this figure are in the Vega system.