The pixels have a bit of "memory" to them, and if they don't do a full on-off cycle they tend to get muddied over time. It's a bit more psychedelic on a color panel, but the same thing happens with Kindle e-readers every handful of page turns.

I had to optimize our product's driver for a monochrome display; you can optimize quite a bit if you know the application and test how muddied it gets and how fast. I think that driver optimizing will be able to make the flashing on the color screen less annoying too.

Hell, the earliest models did a full inversion for every single page turn.

You got used to it after a day or two anyway.