A method senses electromagnetic energy associated with a source over an area in N frequency bands and generates color image data representing at least a portion of the area. The data are arranged as pixels, and the data for a given pixel comprise chroma, hue, and intensity values. The N frequency bands constitute a mathematical basis in N-dimensional space, and one band establishes a first reference vector in the space. Equal parts of all bands establish a second reference vector. A reference plane contains the first and second reference vectors. The data for the pixel correspond to a point in the space, and that point and the second reference vector define a plane of interest. Hue is an angle between the reference plane and the plane of interest. Chroma is an angle between the point and the second reference vector. Intensity is the point's Euclidean norm.