Background colors in Chrome and Atom are no longer uniform Ever since upgrading to macOS Sierra, previously solid background colors in Atom and on certain websites in Chrome are now not uniform. It almost looks like I highlighted stuff with my cursor or something. 

It only happens when I plug my mac into an external monitor. If I am working on just my macbook pro screen, everything is normal. When I plug my HDMI into an external monitor, the non-uniform backgrounds start again — including on my macbook pro screen, if mirrored. The HDMI and monitor were checked with other laptops of mine, and the problem never came up. I also tried a different HDMI with the mac, and same problem.

Certain apps like Safari, do not display this problem at all. I've included a screenshot for example:
Try disabling hardware acceleration on Chrome settings. Turn off filevault, check for icc color profiles. In utilities > ColorSync and verify to see errors. It's the GPU i guess, Chrome will active the discrete GPU. Atom is a Chrome App (not shure?). Hope it helps. Looking for a better solution too.