Lack of Sleep Can Even Affect How You See Colors

According to a study carried out at the  University of Houston in Texas, a lack of sleep can affect how you see colors.
The study involved five people who viewed a full-field, homogenous stimulus of either slightly reddish or greenish hue. The observers had to judge whether the stimulus was greener or redder than their internal perception of neutral gray. Across trials the hue was varied. One pair of monocular tests was performed just before participants went to sleep, and testing was repeated after participants slept for an average of 7.7 hours.
Lack of sleep can make you see the color gray as having a slightly but significantly greenish tint. Overnight sleep restored perception to achromatic equilibrium so that gray was perceived as gray.
According to the authors and principal investigator Bhavin Sheth, scientists had not previously investigated how sleep might affect the way we view the world around us. "Our findings suggest that wakefulness causes color classification to drift away from neutrality, and sleep restores color classification to neutral." In other words, a lack of sleep makes you see neutral colors abnormally and when you are sleeping well again, this color perception is restored to normal.