When you access the Colour Warper from the Colour Corrector and you input a front, back, and matte clip, you can invert the matte to colour correct the region outside the area defined by the matte. Inverting the matte swaps the transparent and opaque areas of the matte and redefines the area of the front image that can be colour corrected, as well as the area of the back image that is shown. To invert a matte, enable the Invert Matte button in the Setup menu.