Have you switched to the “Matte” option under view? It sounds like primate is adding pixels from the inside of your subject to the matte, thereby adjusting the appearance of your color. Once you’ve keyed out your background you need to switch to “matte” view and clean up the inside of your subject that you don’t want to clean up. Hope this helps.
Steve Stone ||
Senior Designer ||
DXD (Post/Design/FX) ||
https://www.d-x-d.com