Colour (left) and concentration index (right) cut of all GC detections (black open circles) and the GC detections within 2R_e (blue circles), based on the spectroscopically confirmed GCs in MATLAS-2019 (red circles: Müller et al. 2021). The light red region highlights the selection cut we used for colour, 0.5 < (m_F606W − F_814W)₀ < 1.2, and for the concentration index, 0.1 < Δm_4 − 8 < 0.5, for galaxies with a distance ≤25 Mpc. For galaxies at larger distances, i.e., > 25 Mpc, the lower concentration index cut was extended to include the unresolved sources, highlighted by the light orange and light red regions, corresponding to a cut of −0.1 < Δm_4 − 8 < 0.5.