Hβo vs Pa_β1.28 line strengths in GCs from the Cen A galaxy and the MW. In this plot, Cen A GCs are represented by filled circles and MW GCs by filled squares. The line strengths are plotted against the [MgFe]′ metallicity indicator, with a bluish colour bar denoting the [MgFe]′ values for Cen A GCs and a reddish colour bar for MW GCs. The overlaid grid shows the predictions of the E–MILES model with BaSTI isochrones. The model grid displays predictions across a range of metallicities for the distinct ages specified in the legend.