You can plot the color value for any pixel in the key color bars. You can then adjust the tolerance or softness range so that the pixel falls within one of the ranges.
To plot a pixel's color values:
Click the Plot picker.
Sample a pixel in the image.
A red bar appears in each of the color bars showing the color value of the pixel that you sampled.
Note: You can change the color of the plot bar in the Setup controls.