1. A color gamut data creating device comprising: a receiving unit that receives measurement points concerning a device, the measurement points being defined in a color space that is capable of representing hue by a hue angle, the hue angle being defined by an axis perpendicular to an achromatic axis that represents lightness; a projecting unit that projects the measurement points on a projecting plane that is perpendicular to the achromatic axis; a first vertex determining unit that determines a vertex of a polygon that is formed based on the measurement points projected onto the projecting plane; a vertex angle determining unit that determines a hue angle of the vertex; a target-plane angle determining unit that determines a hue angle of a target plane based on the hue angle of the vertex determined by the vertex angle determining unit; a locating unit that locates characteristic points based on the measurement points on the target plane; and a data creating unit that creates color gamut data indicative of a color gamut indicative of a distribution range of the characteristic points based on the characteristic points on the target plane.