When it comes to the psychology of eating, food has to look good if it's going to taste good. That's why fast foods contain color additives -- to prevent the loss of a food's inherent color, to enhance color or to add color when it doesn't exist naturally. Hardly a single fast-food menu item doesn't have at least one artificial color buried somewhere in its ingredient list.
Common additives include Yellow No. 5, Yellow No. 6 and Red No. 40. According to one source, Red No. 40, which finds its way into jellies, pastries and those neon-red maraschino cherries perched atop your Chick-fil-A shake, is the most widely used food dye in America. This same source says Yellow Nos. 5 and 6, which provide the golden glow to cheeses, pudding and pie fillings, and soft drinks, are the second and third most common food colorings, respectively [source: Women's Health]. But when we analyzed the ingredients of five popular fast-food menus, we found caramel color to be even more common.
Caramel color is the dark brown material that results from carefully heating food-grade carbohydrates. Just think of the color of sautéed onions (a process known as caramelizing, by the way), and you'll get a good idea of this particular hue, although it can range from reddish-brown to light yellow. Contrary to what you might think, caramel color has no significant effect on the flavor profile of the finished product.
The same can't be said of the next item on the list.