When I use Keylight and i make a mask before I applied klight, klight just dont work!!!I have to apply klight then the mask…maybe on your side it make some other weird thing.And for the replace color, just use “source”.
What i like to do to color correct my keyed footage, is to track matte the original footage with the precomposed keylight setup, this way you have no problem with color.
Hope this help