Slate's Daniel Engber wonders why we praise El Bulli's Ferran Adrià for using xanthan gum but recoil at the use of FD&C Red No. 40 in red velvet cake, and says our aversion to artificial coloring makes no sense:
If the artificial colors are as safe as natural ingredients and they don't taste bad, then why should we avoid them? The gastronome might argue that the chemical dyes impart a color that's unappetizing on its own terms. The garish brilliance of red velvet cake has no referent in nature; it's disgusting because it's fake. Natural dyes, on the other hand, can make food look wholesome and real, by restoring our ingredients to their natural state. If a stalk of rhubarb loses its rosy hue in the saucepan, we add it back by boiling the skins. But to take this distinction seriously, you have to accept the outdated idea that a food has a "natural color" to begin with.
For instance, the fruits we call "oranges" are often green when they're fully ripe. (They turn orange on the tree only when they're exposed to cold weather or bathed in ethylene gas.) The oranges you buy at the supermarket may look natural, but there's a good chance they've been coated with Citrus Red No. 2. Likewise, we're all familiar with the faint, yellowish color of pure butter. (Margarine manufacturers were once penalized for conniving to make their pale-white substitute look more like the real thing.) But thanks to a loophole in the FDA's labeling rules, that wholesome shade is often the result of added dyes.