NUVrK galaxy distribution ouside and inside the green valley, shown in four redshift bins. Top sub-panels: NUVrK diagram as a function of the galaxy stellar mass. The red and blue contours show the equal density of the quiescent and star-forming populations, respectively, after excluding the transitioning galaxies (i.e. the galaxies lying in the green valley defined in Fig. 8). Bottom sub-panels: normalised number counts along the (r−K_s)° colour in the green valley (black solid line). The distribution at 0.2 <z< 0.5 is repeated in each panel for comparison (blue shaded area). The vertical green dashed line shows the limit of the -quenching channel, as discussed in Sect. 7.2.1.