The present article was the representative presentations of our recent results on simultaneous color contrast. Subjects were instructed to make wavelength settings for various hues by an absolute method in the presence of surround-field colors or darkness. Surround- and test-field colors were equated in luminance in one experiment and changed in luminance ratio in the other. In general, the results showed that a shift required in a subject's wavelength setting for the maintenance of an absolute test color occured in the presence of a background color, the direction of the shift being in the direction of the wavelength of the background color. Distributions of wavelength settings for various hues were analyzed and found that they were considered as the normal distribution unchanged in the presence of various background colors and absence of colors. Induced colors were made observable on the central white area. Subjects were asked to detect changes of chromaticity of induced color by increasing luminance of a superimposed test light of wavelength. The data for each of two subjects, color backgrounds, and different luminance levels of the background showed that induced color inferred. .from the change of density settings of a test Light required to perceive the minimum change of chromaticity had a broad effect and spread over the whole range of visible wavelength.