Purpose: To quantify changes in colour vision immediately after exposure to different altitudes of low-pressure hypoxia. Methods: The study involved 35 healthy participants (ages 20–26). Colour vision was assessed using the Farnsworth-Munsell 100-Hue test at eight different altitudes (condition 1: ground, condition 2: 3500 m, condition 3: 3500 m after 40 min, condition 4: 4000 m, condition 5: 4000 m after 40 min, condition 6: 4500 m, condition 7: 4500 m after 40 min, condition 8: back to the ground). Data were analysed using Analysis of Variance (ANOVA), paired t-test, and χ² test . Results: Total Error Score (TES) increased with altitude and hypoxia duration, with higher TES in condition 8 than in condition 1. There were significant TES differences between conditions 3 and 7, as well as 4 and 7. Friedman and repeated ANOVA tests revealed significant sector differences, with Blue-Yellow Partial Error Score (PES) greater than Red-Green PES, particularly on conditions 4, 5 and 8. Significant Red-Green PES differences were found between conditions 4 and 7, and Blue-Yellow PES between conditions 3 and 5, 7, 8. Tritan (Blue-Yellow) shift was most pronounced at high altitudes. Conclusions: This experiment investigated acute low-pressure hypoxia’s effects on colour vision, supplementing chronic hypoxia research. Increased altitudes and exposure duration worsen colour vision, with effects persisting post-recovery. Tritan axis loss is most significant under hypoxia.