This study analyses how contrast sensitivity loss affects colour vision (CV) testing. Eleven participants were scored while cycling through randomly arranged pictures of CV tests with varying levels of contrast changes applied. Hardy-Rand-Rittler (HRR) scores declined significantly at each successive decrease in contrast level after the highest setting (p < 0.004). HRR scores were also lower than those for Ishihara and Farnsworth D-15 tests at two contrast settings (p < 0.01). Contrast changes had the greatest impact on HRR scores, indicating that this test may not be an accurate reflection of CV in patients with contrast sensitivity loss.