The effects of different color signal sequences with the same several colors in the human color impressions were examined. Whether a several-color cyclic sequence has a minimum distance or not in the RGB color space was applied for subjects in an analysis of color sensations. In this study the degrees of pairs of terms applied to color (or color sequence) such as natural-unnatural, pale-deep, and dark-light were investigated. The word natural as a human color impression is, for example, calm,

more »

... owing, relaxed, etc., and the word unnatural is intense, tight, unpleasant, etc. in this case. As the results, the well-ordered color signal sequences with the minimum distance (minimum sequences) showed natural degrees. The random-ordered color signal sequences not having the minimum distance (non-minimum sequences) showed unnatural degrees. In addition, for both non-minimum and minimum sequences, the majority of subjects are impressed with light rather than dark. For pale-deep impressions, they are impressed with deep rather than pale. It seems that the impressions of natural-unnatural, pale-deep, and dark-light are independent. And we proposed a human color impression model using the route area indicated by both hue and saturation.