In this section, you can choose the color to be used to select
pixels that will be concerned by color exchange.
Three sliders for RVB colors: If you
have clicked on preview, they are automatically positioned.
But you can change them. Each slider acts on color intensity.
Input boxes and arrowheads work the same. Result is
interactively displayed in the From swatch box.
Three sliders for thresholds, for each
color. The higher the threshold, the more pixels will be
concerned. Result is interactively displayed in Preview.
Lock Thresholds: This option locks threshold
sliders which will act all the same.