7. The Menus / 7.6 The Tool Menu
You can use Match Colors to adjust the color gamut of an image to a source image.
If there is a mask for the active layer, it can be deactivated via Use Mask.
Brightness and Color control the intensity of the adjustment. If both are 0%, the target image is not changed.
If Destination from Selection only is active, the color gamut of the target image is determined only from the areas selected by the mask/lasso.
Source is used to specify the source image. Again, you determine with From Selection only that the color gamut is calculated only from the selected areas. Use Document to select the document of the source image. There are all open documents available. Layer controls the source image more finely. If a document contains more than one layer, the overall composition is used with All Layers. If the target image is part of the selected document, you can choose Below Active for the underlying layers. Apart from that, there are the image layers of the source document.