Difference between the mean metallicity of 35 GCs with at least 100 stars in the Pristine-Gaia synthetic (circles) and Pristine DR1 (squares) catalogues, compared to the literature values (Carretta et al. 2009), over a broad range of metallicities. The gray bands highlight clusters that are present in both catalogues. Cluster names and metallicities are listed, and the symbols are color-codded by the E(B − V) value toward each GC. The expected zero purple line and the vertical dashed lines are highlighted for visualization purposes.