2 Gyr, [Fe/H] = −0.6 PARSEC/COLIBRI isochrone and the locations on the HR diagram where spectra are generated by local interpolation, global interpolation, or potentially taken from the ‘static’ giant, O-rich TP-AGB, or C-rich TP-AGB sequences. We only switch to the respective sequences when we have reached the bluest average spectrum on that sequence (according to the colour–temperature relation). For example, only the coolest RGB stars (T_eff ⪅ 4000 K) are represented by a spectrum originating from the static sequence, and the spectra of warmer RGB stars are created by the global interpolator.