Normalised histograms of the (m_u − m_F475W)₀ colour of the GCs of MATLAS2019; N is the number of sources in each bin and N_max the maximum of their respective histograms. The red hatched histogram shows the spectroscopically confirmed GCs and the blue histogram the GC candidates. Only sources with trustable magnitude in the u−band are shown (i.e. m_u < 25.8, see Sect. 3.3). The dashed vertical black lines indicate the ±3σ cut applied for GC selection.