Evolutionary tracks of model stars with a metallicity of [Fe/H] = −1 and initial masses of 0.8 M_⊙ (blue line until the helium flash, and then red line from the start of the core-helium-burning phase) and 2 M_⊙ (green) on the colour–magnitude (F606W–F814W, F814W) diagram. The regions inside the grey and cyan lines indicate the RGB and AGB boxes, respectively, introduced by H23. The evolutionary sequences are shown until the start of the post-AGB contraction, which is omitted for readability.