The high degree of yellowness in the 75% O2 + 25% CO2 group was likely due to the high O2 content and consequently higher oxymyoglobin content in this treatment. Unlike the results obtained in the present study, Vergara and Gallego (2001) noted that in lamb, the L* value of Longissimus dorsi muscles significantly increased over time in samples stored in either 20% CO2 + 10% O2 + 70% N2 or 80% CO2 + 20% O2, with values ranging from45.32 to 48.92. This observation was likely due to protein denaturation, which increased its dispersion of light (Insausti et al., 2001). Furthermore, a* values decreased significantly in these atmospheres, with values between 11.99 and 16.55. The reported b* values were greater than in oxygen-free packages, ranging from 7.72 to 11.85. The L* in the present study was similar to that observed by Luciano et al. (2009) when assessing the color stability of the Semimembranosus muscle of the same species stored in 80% O2 + 20% CO2 for 14 days at 4 °C. Furthermore, Berruga, Vergara, and Gallego (2005) noted that vacuum-packed samples exhibited greater color stability, noting that L* and b* values were higher in the treatment containing high O2 levels, whereas the a* values were lower.