Morphometric parameters used for the selection of GC candidates: CI, elongation, and (g − r) colour are shown in the top left/middle panels, bottom left and middle panels, and top right panel, respectively. Grey dots represent all sources in the gr-matched catalogue, while red dots indicate GC candidates within R_e, GC of NGC 5018 (see Sect. 5.2). The dashed vertical and horizontal black lines indicate the adopted range for GC selection (see Table 3). The black error bars in all the panels denote the median error on magnitude (multiplied by a factor of 7 for visibility purpose) with a bin size of 2.0 mag, and on (g − r) colour (top right panel) within the given magnitude bin size.