What is Yellow 6?
Yellow 6 also known as Sunset Yellow FCF or Orange Yellow S is an artificial food colorant. 
It is a synthetic coal tar and azo yellow dye useful in fermented foods which must be heat treated. 
Synthetic food dyes have been suspected of disrupting children's behavior since the 1970s, when Dr. Ben Feingold, a San Francisco allergist, reported that his patients improved when their diets were changed. Numerous controlled studies conducted over the next three decades in the United States, Europe, and Australia proved that some children’s behavior is worsened by artificial dyes, but the government did nothing to discourage their use and food manufacturers greatly increased their reliance on them.