Good to see the first comment there corrects him, and that it's not actually green pixels; at least for the Intel and nVidia drivers I've used before, it appears to be more of a dark magenta. It could be configurable or hardcoded somewhere in the driver, but I don't think it's fixed in hardware.

The desktop compositors takes the graphics content of all the windows, including their composition visuals, and combines them to form a full desktop image that is sent to the monitor.

...at the cost of latency and efficiency.