Colour–magnitude tracks traced in the HDR by representative CVs with unstable accretion discs. Two sets of tracks are plotted, corresponding to P_orb = 88 min (bottom set, pinkish colours) and P_orb = 6 h (top set, bluish colours). Three tracks are plotted in each set, corresponding to three different mass transfer rates Ṁ_t. The dots on each track regularly sample the outburst cycle over time. The light curves are shown in Fig. B.1. The green rectangles delimit the upper and lower hook regions defined in Fig. 2.