Oxalyldihydrazide as a fuel was used to prepare new nano size blue refractory ceramic pigments MgAl2O4: xCo2+ (0.00 ≤ x ≤ 0.10) using low temperature combustion synthesis (LCS) method. The synthesized and calcined powders were characterized by Fourier transform infra red (FTIR) spectrometry, electronic spectra, thermogravimetry, differential thermogravimetry, differential thermal analysis, X-ray diffraction (XRD) analysis, and transmission electron microscopy (TEM). Also, the color measurements of nano pigments are studied by diffuse reflectance spectroscopy (DRS) using CIE-L*a*b* parameter method. The FTIR spectra show frequency bands in range the 422–700 cm−1 correspond to metal oxygen bonds through vibrations for the spinel structure compound. The average particle size of prepared samples as determined from XRD and TEM was 30 nm at 1100 °C. Also, the results revealed the varying bulk density, particle size, shape and color with different calcination times and temperatures.