The cause of existing misunderstanding is clarified on the Helmholtz-Kohlrausch (H-K) effect. The misunderstanding is that the effect is the same in magnitude between the variable achromatic color (VAC) and the variable chromatic color (VCC) methods. It comes from the confusion between a single observation and a complete experiment. If both methods are tested in a proper experiment with sufficient observations, then the methods do give different results. The present communication together with a previous article (Color Res Appl 2006; 31: 146-155) will clarify the differences between VAC and VCC methods. For readers' convenience, a simple and accurate experimental method is proposed for grasping the large effect of the VCC method. (C) 2008 Wiley Periodicals, Inc.