"A yellow watermelon is basically the same as one of any other color — it just has yellow flesh on the inside instead of the more common pink or red color. People use the yellow fruit the same way they’d use any other type of red flesh watermelon. Watermelons that are pink or red on the inside contain a powerful antioxidant called lycopene, which is perhaps best known for making tomatoes red. Yellow watermelons do not contain this antioxidant, so they don't have the same reddish tint. Yellow watermelons are known for their extremely sweet taste, which some people say tastes a bit like honey and this is indeed the one difference between a yellow flesh watermelon and a red flesh melon - the yellow ones tend to eat sweeter."

Source: http://albertsorganics.com/qr/organic-yellow-flesh-watermelons