Color plays an important role in information visualization. To use the colors as visual representations of the data effectively, designing color schemes that consider perceptual differences between colors is necessary. We developed a tool to assist in color-scheme design when using the CIE1976L*a*b* (or CIELAB) color space. The developed tool provides functions to assist in designing color schemes for nominal, ordinal, and quantitative data. The CIELAB color space has a property in which the Euclidean distances between any two colors in the space can approximate the perceptual differences between them. Thus, designing color schemes for data representation is convenient. However, because the CIELAB color space has a distorted shape, color scheme design in such space is not easy. Our tool allows the designer to see the positions of colors in the CIELAB color space visually to facilitate scheme design. Moreover, our tool provides information to the designer on the distinguishability of the selected colors, and offers functions to correct color schemes automatically.