Observational footprint of this study. The GC sample is marked with either orange diamonds or blue circles, signifying GCs with and without robust reddening estimates. EXT8 is marked in red, and the black circles are confirmed M31 GCs from the C&R16 catalogue that were not considered. The background colour is the reddening from the Schlegel et al. (1998) dust map with the correction of Schlafly et al. (2010), clearly highlighting M31 itself. The two rectangles with ‘ears’ are the observed fields that form the footprint for this study.