An important finding in the present study is that "zero-grayness luminance" proposed by Evans gives approximately the same perceived brightness for spectrum colors irrespective of hues. The luminance values with the same perceived brightness for spectrum colors are directly derived on the basis of VCC method proposed by the senior author. It corresponds to the spectral luminosity function V-b2(lambda;VCC)- In the study process, we had some doubts on the luminosity function CIE V-b2(lambda) on the heterochromatic brightness match. In other words, CIE V-b2(lambda) may not be used for scientific study. The problem is discussed in Appendix briefly. (c) 2007 Wiley Periodicals, Inc.