Using the Palette Property Trackbars
The lower portion of the Palette Manager has a tab sheet for adjusting the properties of the color channels. There is one tab each for the R, G, and B channels and for adjusting all channels at the same time.
Open the Palette Properties dialog.
Select the desired color channel from the Color Channel tabs. If you do not see the tab control in the bottom half of the window, click [Show >>].
Move the trackbars to change brightness, contrast, and gamma.
Moving the trackbars on the R, G, and B channel preferences pages changes the value in an absolute sense between 0 and 100%.
On the All channels preferences page, the trackbars adjust the R, G, and B properties in a relative sense, starting from their beginning values.