This study describes a color enhancement method that uses a color palette especially designed for protan and deutan
defects, commonly known as red-green color blindness. The proposed color reduction method is based on a simple color
mapping. Complicated computation and image processing are not required by using the proposed method, and the
method can replace protan and deutan confusion (p/d-confusion) colors with protan and deutan safe (p/d-safe) colors.
Color palettes for protan and deutan defects proposed by previous studies are composed of few p/d-safe colors. Thus, the
colors contained in these palettes are insufficient for replacing colors in photographs. Recently, Ito et al. proposed a p/dsafe
color palette composed of 20 particular colors. The author demonstrated that their p/d-safe color palette could be
applied to image color reduction in photographs as a means to replace p/d-confusion colors. This study describes the
results of the proposed color reduction in photographs that include typical p/d-confusion colors, which can be replaced.
After the reduction process is completed, color-defective observers can distinguish these confusion colors.
A method to specify and quantify undertone is proposed based on CIELAB color space. This method enables us to deal with colors according to their undertones (their ratio and Lab coordinates). The method also enables us to discuss undertone from the viewpoint of color appearance, being isolated from personal color analysis.