AW3225QF, makes windowed video reddish

I just got this:

Alienware 32 4K QD-OLED Gaming Monitor - AW3225QF

When I open a Youtube video and it seems when window it, the colors are off and people's faces are red. If I maximize the window, the colors are good. I've never seen this effect before.  It looks like it's modifying the colors of that video display part of the screen. What's it doing?

Thanks.