Humans Can Only Distinguish Between About 30 Shades Of Gray Alison Bennett03/10/201506/22/2015FYI Post navigation PreviousNext http://www.popsci.com.au/science/medicine/humans-can-only-distinguish-between-about-30-shades-of-gray,400746 Humans Can Only Distinguish Between About 30 Shades Of Gray Advertisements Share this:TwitterFacebookLike this:Like Loading...