Fark up your brain for a few weeks.
This is the WMD of optical illusions. Look at an image of black bars over a colored background, and for a few hours or days, you will see all black bars to have a faint haze around them. Use this information at your own peril.
Goddamn, it has been almost a day and it is still there!
Almost 2 days, only a faint hint is still there.