Effect of Route Complexity of Spatial Color Sequence on Human Color Impression and its Fuzzy Model

We examine how a toroidal sequence of the six fundamental colors affects human color impression. In order to investigate the different effects of spatial color sequences, we consider a hexagonal diagram that is a projection of RGB color space. The hexagonal diagram corresponds roughly to the hue circle indicated by both hue and saturation. The toroidal sequence is similar to the hue circle. The projected route area indicates the magnitude of naturalness (as in rainbows) for color sequences. The minimum sequence is similar to the order of colors in rainbows, whereas the non-minimum sequence is completely different. Therefore, we propose a simple fuzzy model of human color impression using the projected route area assisted by route complexity. The complexity is defined by the ratio of the square of envelope route distance to route area. The relationship between route complexity and the number of subjects for projected route area is investigated. We clarified that the majority (approximately over 26%) of subjects of nearly all ages have natural impressions when the minimum route area is large, and propose a simple fuzzy model of the human color impression. This model provides the natural (or unnatural) order of spatial color sequences of several colors.