(m_F475W −m_F606W)₀ vs (m_F606W −m_F814W)₀ colour-colour diagram of GC candidates, colour-coded with the (m_u − m_F475W)₀ colour. The 20 spectroscopically confirmed GCs (Müller et al. 2020; Haacke et al. 2025) are shown as squares and the candidates as circles. The size of the marker indicates the m_F606W of the source, as shown in the legend. The sources in grey are objects that are too faint to be measured in the u-band. The blue open circles highlight those objects rejected based on their (m_u − m_F475W)₀ colour.