The variations in the color of a test field of constant luminance during changes in the luminance of a contiguous inducing field was measured psychophysically. The fields had the same hue (red, green, or blue). The colors induced in the test field could be specified by the strength of a chromatic quality, and by the strength of the opponent qualities luminous/black. The psychophysical relationship between the two kinds of perceptive variables and test and inducing luminance followed distinctly different functions. The luminous/black variable varied linearly with contrast over a large range, as previously found for achromatic colors. The contrast gain of the luminous/black variable for the red and green colors was the same as for achromatic colors. The gain for the blue colors was twice the gain for the other colors. The chromatic variables were primarily related to the local luminance. For a given test luminance they were maximal near zero contrast. They followed the same function as the white component of achromatic colors. It is suggested that the luminous/black variable is related to spectrally broadband cells with a strong center/surround antagonism, while the chromatic variables and white are related to cells that lack a spectrally broadband surround in their receptive field.