Color edit tool, choose color or erase saturation
Tool to change the color of a selected area or layer while in Foreground, Background, or Erase modes.
Possibly programmed to utilize the existing Color Spectrum palette (found in the initial select type-of-background function), by linking the Palette as a tool in another mode.
A masking brush needs to be created that removes the color from the areas. Desired. If you wanted to get deeper, instead of taking all color and saturation, maybe you could also allow it to remove the displayed color and apply shades of blue, shades of red, and shades of other colors, and not just grey scale.
Similar to "magic select" tool in Adobe PS/CS/CC.