Thank you for writing this. At first I really downloaded game directly from gog website, without using gog galaxy. After I downloaded and installed game via gog galaxy, pink screen disappeared.
I have latest versions of PoE (2.13.0.18) and both additions white march I and II (3.06.2.54) from gog.com and I have a pink screen when I enter the white march. Re-installation of the game and additions didn't help. The patches available on gog are elder than my installed version. I have Windows 7 64.