This filter is found in
→ → → .Unlike Exchange filter, Map Color Range maps a defined color range against another defined color range.
Preview: This Preview displays color changes interactively, before they are applied to Image.
The two Color Swatch Boxes allow you to define From and To limits of source color range. Default colors are the Foreground and the Background colors of the Toolbox, but, when you click on a box, you call the Gimp Color selector which lets you select other colors.
The two Color Swatch Boxes allow you to define From and To limits of destination color range. When you click on a box, you call the Gimp's Color selector.