Looking at my monitor pixels with a good loupe, the gray is made of red+green pixels in a Bayer pattern. So the scrolling is making a purple effect, probably in

Looking at my monitor pixels with a good loupe, the gray is made of red+green pixels in a Bayer pattern. So the scrolling is making a purple effect, probably in our aforementioned weird human visual system. update: Bayer pattern is wrong term. The MacOS background is a red+green checkerboard. The HN background is a vertical stripe of red+green.