This study analyses the effect of contrast sensitivity (CS) loss on colour vision (CV) testing, using a variety of colour vision tests. The authors used a computer model for CS loss to determine its effect on CV testing scores for the Ishihara and Hardy-Hand-Rittler (HRR) tests when compared with the gold standard colour vision Farnsworth D15 test. A total of 11 participants were scored while cycling through randomly arranged pictures of CV tests with varying levels of contrast changes applied. HRR scores declined significantly at each successive decrease in contrast level after the highest setting. HRR scores were also lower than those for Ishihara and D15 tests at two contrast settings. The authors conclude that 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. The authors acknowledge the limitations of their study, including the small study population and the use of the Farnsworth D15 as gold standard instead of the Farnsworth-Munsell 100 test. They also acknowledge the requirement for future studies using patients with ocular pathology to allow a direct examination of the impact of CS loss. However, from the results of this study, clinicians should be cautious when interpreting results from HRR tests, especially in patients with disorders that are known to affect contrast sensitivity.