http://www.lifeslittlemysteries.com/2612-color-red-blue-scientists.html?fb_comment_id=fbc_10151081421809073_25866878_10151252075864073#f891c5bd
Anyone with normal color vision agrees that blood is roughly the same color as strawberries, cardinals and the planet Mars. That is, they're all red. But could it be that what you call "red" is someone else's "blue"? Could people's color wheels be rotated with respect to one another's?