Oxalyldihydrazide as a fuel was used to prepare new nano size blue refractory ceramic pigments MgAl2O4: xCo(2+) (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 degrees C. Also, the results revealed the varying bulk density, particle size, shape and color with different calcination times and temperatures. (C) 2010 Elsevier B.V. All rights reserved.