To date, brilliant-blue pigments that can maintain outstanding stability in a corrosive environment over 1273K are still very desirable in the ceramic industry. We systematically investigated the structural, optical, colorimetric and thermal properties of a novel type of CoNb2O6 pigments, which have the 6-fold coordinated Co2+ as chromophores and high-valent Nb5+ as the mainstay factor for structural stabilization. Effective coloring contribution from different visible-light regions, the coloration mechanism and thermal stability of the pigments applied in glaze at 1273–1473K are revealed for the first time. The Co2+ cation at the distorted [CoO6] octahedra generates the brilliant blue hue, which can maintain the absolute blueness values, b⁎, at 30–44 even after glaze calcination at 1273–1423K. The superb thermal performance in a harsh environment of the CoNb2O6 pigments significantly outperforms the classic CoAl2O4 blue, thereby exhibiting attractive prospects for high-end blue-sky–hued decoration for ceramics.