While pink lemonade is usually made by taking lemonade and adding food colorng, or natural color changers like pomegranate or cranberry juice. Real Pink Lemons do exist! Variegated pink lemons come from the Eureka Lemon tree, and are a mutation of the common lemon featuring the same yellow outside, but inside, they're pink! In double blind taste tests, subjects could not tell the difference between pink, and "regular" lemons. So it's just the color! Why are they pink? Scientists aren't completely sure, but my hunch is that it has something to do with human sacrifice!
(Edited 2 minutes later.)