Zn_1-<i>x</i>Co_<i>x</i>MoO₄ (<i>x</i> < 0.3) compounds prepared by the solid-state route crystallize in a triclinic unit cell with the <i>P</i>t space group. X-ray diffraction and Rietveld analyses reveal the occurrence of three highly distorted sites with equal occupancies corresponding to one trigonal bipyramidal CoO₅ group and two octahedral CoO₆ groups occupied by either Zn²⁺ or Co²⁺. Mo⁶⁺ ions are located in distorted tetrahedral sites. Electron paramagnetic resonance analysis allows characterization of the two kinds of environments with orthorhombic distortion related to two signals with different <i>g</i> values. The UV-vis spectra exhibit intense Co²⁺ d-d transitions associated with CoO₅ and CoO₆ chromophores between 1.9 and 2.6 eV in the visible domain and O-Mo charge transfer at the frontier between the UV and visible ranges. A blue-transmitted window can then be displayed. The formation of covalent MoO₄ entities and polarizable Zn²⁺ cations creating highly distorted noncentrosymmetric sites partially occupied by Co²⁺ allows stabilization of the first blue pigment without Co²⁺ in the tetrahedral environment. Moreover, only 5-10% cobalt is necessary to get a strong blue hue because of the highly distorted sites leading to very important oscillator strengths.< Leer menos