The window lets you perform color correction on paint layers.
To open the window, select 
in the window.
options
HSV
Adjust , , and settings for the selected paint layer.
Curves
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Select the channel whose curve you want to edit. Select from , , , , , or channels, then adjust the corresponding curve.
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Reverts any changes you've made to the curve for the selected channel, and resets the curve to a default straight line.
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When on, you can preview adjustments to the curve as you adjust curves.
