Average [Mg/Fe], [α/Fe], and [Mg/α] of our collected GES and literature sample of 28 MW GCs (green circles, see Sect. 4) and of the literature sample of extragalactic GCs (purple squares; see Sect. 4.3). The MW reference population is drawn from the GES iDR4 sample (black dots) and from the SAGA database of metal-poor stars (grey dots). We also plotted NGC 2419 as a yellow upward triangle and Ru 106 as a yellow downward triangle.