Solid solutions of Mn and Mg mixed diphosphates Mn 2-x Mg x P 2 O 7 (0.2 < x < 1.5) have been prepared by calcination (1000 °C/4 h) of coprecipitate precursors and characterized for the first time (through thermal analysis, XRD, SEM/EDX and UV–vis-NIR techniques). Its colouring performance (CIE- L * a * b * parameters) within a ceramic glaze has been also analyzed. XRD and SEM/EDX results confirm the formation of a homogeneous and continuous β-Mn 2-x Mg x P 2 O 7 solid solution having the thortveitite structure, isomorphous to β-Mn 2 P 2 O 7 and β-Mg 2 P 2 O 7 . The diphosphates exhibit light brown or pinkish-white colours associated to Mn 2+ ions in low-symmetry octahedral coordination. Interestingly, they develop intense purple ( x < 1) or pink (1.0 ≤ x ≤ 1.5) colours once enamelled (5 wt.%) within a single-firing ceramic glaze, which are mainly associated to the presence of Mn 3+ ions according to UV–vis-NIR spectra. Therefore, the Mn–Mg binary diphosphates could be used as new pink ceramic dyes for the colouration of conventional ceramic glazes.