If you click a wire going between an output bitmap node and the Compositor Output node, you're prompted to insert a Color Correct node.
This node, labeled "Color Correction," modifies the output bitmap image with four basic parameters:
- HueShift
- Saturation
- Contrast
- Brightness
Each parameter has a numeric setting that you can change with the keyboard after double-clicking it.
As you change the Color Correct node parameter values, its thumbnail and output update in real time.
Note: You can also create a Color Correct node from the Compositor menu and the main right-click menu in Compositor View. In such cases, the new Color Correct node might appear outside the visible portion of the Compositor View window, but you'll still be able to see it in the "radar" (navigator view in the top-right corner). If that happens, use Auto-Layout Nodes from the Compositor menu to bring the nodes together.