The methodology by which the magnitude of a measured color difference (DELTAE*) is broken down into changes in perceptual color attributes, lightness (DELTAL*), chroma (DELTAC*), and hue (DELTAH*) is critically examined. Evidence is presented which shows that the definition of hue difference (DELTAH*) would only hold if hue change were independent of any change in chroma, which it is not. A new definition of DELTAH* provides a psychometric hue difference independent of chroma.