Ok, have spent the last hour clicking on and hovering over every text, instruction and icon, and I have discovered the answer. It's done by clicking on the little face icon to the right of the word sharpen, and then another mini-panel with color swatches comes up in the bottom left hand corner, and you can chase the color there. And clicking on that mini-icon also brings up another panel where you can choose auto-mask or various brush options. But if you go back to the main image while that is open, the mask suddenly goes to the whole image. Anyway, if you keep the mouse or trackpad arrow over on the sharpen panel it seems to work. Then you can go back to the left hand little icon next to the word sharpen, and that brings up the sharpening options as before.