(m_F475W − m_F606W)₀ vs (m_F606W − m_F814W)₀ colour-colour diagram of the initial sample of GC candidates. The 20 spectroscopically confirmed GCs (Müller et al. 2020; Haacke et al. 2025) are shown as red squares. The orange dashed box indicates the region we have selected for our next sample of GC candidates and corresponds to ±3σ around the median colours of the confirmed GCs (excluding the anomalous object, see Sect. 3.3). The violet star, and its error bar, shows the prediction from Bruzual & Charlot (2003) models for an SSP of [Fe/H] = –1.44 dex and 9.1 Gyr (Müller et al. 2020). The inset shows a zoom-in into the dashed orange box for ease of viewing. The error bars shown in the upper-left corner are the errors of an object located at the peak of the GCLF (m_F606W = 23.77 mag, assuming a distance of 20.7 Mpc to the galaxy).