ABSTRACT: Aim: The aim of this study was to evaluate the optical behavior of tooth color using CIE L*A*B* space; the teeth were subjected to novel bleaching gels containing peroxide carbamide with potassium oxalate. Materials and Method: Three different carbamide peroxide gels were experimentally fabricated. They consisted of 10% (G10), 16% (G16) and 37% (G37) concentrations. Sixty recently extracted premolars were subjected to different bleaching protocols. Color change (ΔE) was assessed using the CIE L*a*b* system after the application of each gel. The data were analyzed using one-way ANOVA with Tukey’s post hoc test (α=5%) and a t-test. Results: The G10 and G16 gels exhibited an increase in ΔE*ab parameters from T0 to T1 (T0: application day of the gels. T1: 14th day measurement); a small decrease from T1 to T2 was also noted (T2: control measurement, 28th day). However, no statistically significant differences were found (p=0,22 for G10 and p=0,10 for G16). The G37 gel also exhibited an increase in ΔE*ab parameters, with similar results after the first application of 45 min, the second application of 45 min, and the third application of 45 min (T1, T2 and T3, respectively. T4: control measurement, 14th day). No statistically significant differences were observed between the three times of application (p>0,69), and an appreciable difference was noted between times T3 and T4 (p=0,000). Conclusions: The presented formulations of peroxide carbamide at 10%, 16%, and 37% are clearly effective. The G10 and G16 gels exhibited better effectiveness than the G37 gel.