YRGBK 2.3 – Shadow and Highlight color
The shadow color and highlight color options are designed to be used to increase the amount of colorprinting under the Black and White, respectively. These adjustments are limited to the darkest and lightest areas of the image, and only modify the color channels.
Increasing the color printing in the shadows helps to make a richer print with better dynamic range, and allows us to use a lighter touch and a sharper squeegee when printing the Black. In some cases, if there are light areas of color that need a bump, increasing the color printing in the highlights can help.
Generally, I have found it is helpful to bump up the colors in the shadows. This allows for more colorful shadows and deeper blacks. Highlight areas rarely require a boost to the color. If an image is mostly light or pastel colors, however, this option may be helpful.