The P cell pathway in primates is involved in both luminance and chromatic perception. This correlates well with P cell receptive fields, which are both spatially and chromatically opponent. Since, however, the luminance and chromatic channels found in psychophysics are independent, the mixed luminance and chromatic information in P cell signals must be demultiplexed in cortex. We have examined the ability of an unsupervised neural network to demultiplex P cell signals, using realistic visual inputs. Digitized images, corrected to be statically similar to retinal images, were sampled by a simulated retinal mosaic, and filtered by difference-of-Gaussians P cell receptive fields. The simulated P cell signals were used as inputs to a network designed to maximize unit responses while minimizing the correlation between units. After a period of training, we evaluated the receptive fields formed in the network. The neurons clearly fell into two categories. The first were those sensitive to changes in intensity in the retinal image; that is, luminance selective units. The second were those sensitive to a color difference in the retinal image; that is, chromatically selective units.