“What happens when a physicist decides to become a chef? If they’re anything like Manuel Linares, then you can expect a fusion of food and science to come out of their kitchen. He calls it the Xamaleón, a play on the Spanish word for chameleon, and it originally starts as a periwinkle blue frozen treat until it’s spritzed with Linares’ ‘love elixir,’ a super secret mixture he concocted himself. This mixture reacts to changes in temperature and saliva, causing the tutti-frutti-flavored ice cream to turn into purple, then into pink as you lick. He also plans to whip up ice cream that turns from white to pink, and another one that glows under ultraviolet light.”
http://www.engadget.com/2014/07/29/ice-cream-changes-colors/