A statistical approach to account for psychophysical phenomena in human colour vision is presented. The central visual processor is viewed as an optimum recognizer of stochastic patterns supplied by the periphery. The processor makes an optimum estimate of the spectral parameters of the stimulus, given the wavelength filter characteristics of the periphery, the stochastic nature of the information and an internal template to which the external stimulus is matched. The estimate is constrained in ways inferred from empirical phenomena. Subjective brightness of monochromatic stimuli and related constant brightness manifolds in the colour space constitute the constraint for brightness estimation. Results analogous and in accord with those of earlier line element theories are obtained. The Bezold-Brucke hue shift constitutes the basic constraint for hue estimation. The hue estimate involves interrelation between the fields in the experiment. Similarities and differences both in basic conceptions and results introduced by the template matching notions are discussed.