Spinel is a precious gem known for its vivid color and fame in historical record. Colour changing is a common optic phenomenon in gemology normally seen in alexandrite, sapphire, spinel, garnet, etc. The colour changing in gemstones could mostly be attributed to chromium ions and vanadium ions, but there are few reports on color-change spinel, and there is a lack of research on color-causing elements and discoloration mechanism. The subjects of this study include an color-change spinel (blue under D65 illumination, violet-blue under A illumination) and two blue spinels without discoloration effect (there is no significant change in tone under the two light sources). The spectral details and chemical composition of spinel samples could be obtained via laser-ablation ion-coupled-plasma mass spectrometer (LA-ICP-MS), ultraviolet-visible-light spectrometer, Raman spectrometer and photoluminescence spectrometer. Compositional analyses of LA-ICP-MS show that all three samples are magnesia-alumina spinel, the main chemical components are MgO and Al₂O₃ and contain trace elements such as Fe, V, Cr, and Zn etc. The concentration of Fe ion in the color-change spinel is relatively higher, while there is an only minute amount of concentration of Co ion, and the content of V ions in the color-change spinel is similar to that in the blue spinel. UV-Vis spectrum of the color-change sample reveal several absorption peaks: 387, 461, 478, 527, 559, 590, 627, 668 nm.The spin causes the absorption peaks at 559, 590 and 627 nm allowed transition ⁴A₂→⁴T₁(⁴P) of the d electron spin of Co ion and split by spin-orbit coupling. In addition, the Fe²⁺d-d spin forbidden transition⁵E(D)→³T₁(H) in tetrahedral coordination also produces an absorption peak at 559 nm. Specifically, the absorption band around 559 nm, which resulted mutually from Fe ion and Co ion, is the principal reason of color-change effect in spinel. A comparison of Raman spectra shows no difference between the color-change spinel and the other two blue spinels, where the Raman displacement of 311, 405, 663 and 765 cm^-1 correspond to F_2g(1), E_g, F_2g(3) and A_1g vibration, respectively. Photoluminescence analysis of the color-change sample shows that the energy level ⁴T₁(P) of Co²⁺ ion in T_d symmetric position subdivides into three secondary levels. 686, 650 and 645 nm luminescence peaks are generated as electrons drop from excited states of these three ⁴T₁(P) sub-levels to ground state of ⁴A₂(F).The content of Co ion in color-change spinel is very low, and the content of Fe ion is high. Due to the fluorescence quenching of the Fe ion, the sample has no red luminescence.