The present study considers a fuzzy color system in which three membership functions are constructed on the color triangle and the tone triangle. These systems can process a fuzzy input to a color triangular system and to a tone triangular system and output the center of gravity of three weights associated with respective grades. Three membership functions are applied to the color triangle and the tone triangle relationship, respectively. By treating three coordinates of redness, greenness, and blueness on the color triangle and of chromaticness, whiteness, and blackness on the tone triangle, a target color can be easily obtained as the center of gravity of the output fuzzy set. The subjects are required to determine whether the color word for each color is suitable. The response of subjects can be obtained as fuzzy sets (as the membership values of subjects) on the color triangle. The responses for color words (e.g. red) show a mountain-like shape. The height of fuzzy set indicates possibility of a target color or degree of cognition for a target color and the expanse of fuzzy set shows vagueness.