In a color perception experiment, we found that, in CIE perceptual color attributes terms, the darker (lower L*) of a pair of highly chromatic colors of the same chroma (C*_ab) appear to be more colorful. We further derived a model to factor in L* along with C*_ab to describe the perceived colorfulness. In cross media color gamut mapping, it is often desired to reproduce highly chromatic colors to be as chromatic as the system can produce. We apply the found relationship to gamut mapping in the CIELAB space to demonstrate that we can map colors of high C*_ab to darker colors to create the effect of a more colorful, more chromatic mapping.