Most artificially colored foods are colored with synthetic petroleum-based chemicals—called dyes—that do not occur in nature. Because food dyes are used almost solely in foods of low nutritional value (candy, soft drinks, gelatin desserts, etc.), a good rule of thumb is simply avoid all dyed foods.
Diacetyl is one of the many chemicals that give butter its characteristic flavor. Low levels are present in butter (including unsalted butter, to which extra diacetyl is added to prolong its shelf life).
