Running OS X Yosemite on a mid 2012 13-inch MacBook Air, I've noticed that flashing bars will occasionally appear on the screen for no apparent reason. Sometimes these bars are solid colors (often green) or occasionally a sort of weird interlaced black and grey. These bars do not interfere with normal computer operation, and can often be cleared by forcing that portion of the display to refresh, such as by moving a window over it. However, rarely, these bars will cover the whole screen and refuse to disappear.
I am not aware of a way to reproduce this issue, and in all cases restarting the computer resolves the issue. It can appear on both the laptop's display and any connected external display.
I have confirmed this issue with another person who uses the same model of computer. Has anyone else seen this issue? Is there some way to prevent it from recurring?