Colour vision models require measurement of receptor noise and the absorbance of visual pigments, oil droplets, and ocular media. We have studied how variation in these parameters influences colour matching, spectral sensitivity, and colour discrimination predictions in four bird species. While colour match predictions are sensitive to variation in visual pigment and oil droplet absorbance data, discrimination predictions are mostly sensitive to variation in receptor noise. Ocular media transmittance influences only modelled spectral sensitivities at short wavelengths. A comparison between predicted and measured spectral sensitivities in domestic fowl and duck revealed large discrepancies, likely because of influences from achromatic mechanisms.