A model of human visual perception is described. An observer is represented having no a-priori preference for color or geometric properties of the objects in his visual field. The model includes computational representations of effectiveness and efficiency of visual memory allocation that are both based on likelihood. In the computations, the colorimetric quantities color difference, chroma, and lightness are of fundamental importance, being the state variables of model. Computer experiments are carried out verifying the validity of the model. Multiple corroborations between model outcome and commonly observed phenomena are pinpointed, indicating that aesthetical experience denotes an optimal state of visual system as to processing efficiency.