Several times during my maiden Witcher 3 run-through the colors have turned bright purple, probably because a color channel (green?) has dropped out. The only solution is to go back to my previous save, after which the game is fine for awhile. But now I'm trapped: when I enter Crow's Point for the burning-stable scene, the screen automatically turns purple, and does not seem to return to normal afterwards. And this is a main quest, so there's no escape. How can I avoid or fix the purplization of my Witcher 3 run-through?

I should note that my graphics are unusually antiquated: I'm playing on a 2015 MacBook Pro with Porting Kit. It comes with an internal graphics card (Intel Iris Graphics 6100). Frankly, I'm amazed that Witcher 3 runs at all. But if it's going to run, I'd like it to run in full color, thanks!