Purpose: To investigate the effects of real and simulated age-related changes in crystalline lens yellowing on Farnsworth-Munsell (FM) 100 hue performance. Methods: FM 100 hue total and partial error scores (PES) were measured in a group of younger (n = 10, mean age = 22.2 +/- 2.65 years) and a group of older (n = 10, mean age = 54.5 +/- 2.64 years) normal observers along with psychophysical estimates of crystalline lens optical density and pupil size. Three younger observers underwent repeated FM 100 hue testing under a variety of simulated age-related lens yellowing conditions, using filters with well-defined transmittance properties which attempted to mimic the real age-related lens yellowing changes of the older group. Results: FM 100 hue total and PES were significantly higher in the older age group compared with the younger group (p < 0.01). Lens density measures were significantly higher in the older age group compared with the young group (p < 0.01), but showed less scatter than individual FM 100 hue error scores. Simulated lens yellowing in the three younger observers, equivalent to the level of that of the older observers, did not affect any of their FM 100 hue total or PES. Conclusions: Simulation of age-related lens yellowing in younger observers has little effect on FM 100 hue error score. A variety of other factors such as pupil size, background illuminaton level, iris colour and macular pigment density may contribute to the age-related increase in FM 100 hue scores.