Adjust Skin Smoothing question

[caspia1]

Ref 2020 Ultimate.
If I apply skin smoothing to a color image it works fine. However, when I try to apply it to a black and white image it doesn´t work. Is there a reason for this, please, and how can I overcome it?

[Jean-Luc]

Color smoothing is applied to the color of a face. PSP doesn't recognize what is flesh, hair, eye in an image. But it recognizes where flesh color exists and applies smoothing to this area.
Apply flesh color to your B&W image and remove it after smoothing.

[caspia1]

Many thanks for this.