Just got a brand new 4k iMac. I noticed almost immediately when watching YouTube videos that when I scroll down and then scoll back up to the video, there are moments when the picture suddenly becomes saturated/red and then quickly goes back to normal. It's fairly reproducible and I tried on many different YT videos, with the same momentary saturation. I recorded as best I can and caught two instance of this happening. It starts to happen at 0:05 and at 0:12. If you pause it at 0:06 and 0:14 you will see the color shift. Anyone know what this could be? I have other PC's and Macs and when comparing the same videos none of the others seem to exhibit this behaviour.