Most colour appearance models (CAMs) have been developed to predict the colour appearance only for related colours in different viewing conditions. More recently, CAMs to predict for unrelated colours have been proposed due to the availability of the experimental data. This paper investigates the performance of the three promising colour appearance models for unrelated colours, i.e. CAM15u, CAMFu and CAM20u using an experimental dataset carefully accumulated by Fu et al. in term of CV values. The results showed that the latest CAM20u outperformed the other models. CAMFu, as the oldest model, whose performance was much worse than other two models in predicting brightness and colourfulness, and performed well in predicting hue composition, while CAM15u gave a moderate performance in predicting brightness and colourfulness, but performed slightest worse than the others for hue composition.