Why Are Red Onions Considered Red?

Among the greater modern culinary mysteries: why are certain fruits and vegetables (red onions, red grapes, and red cabbages among them) called red when, in fact, they're clearly purple? Actually, this cooking query is so common that it's popped up fairly frequently on Twitter over the past few years. And not without good reason; the confusion surrounding the red onion's name is fairly understandable, given that modern English provides us with dozens of words to describe every hue of color, including the reddish purples that "red" onions tend to display. However, once you understand the history behind how English (and, in fact, most languages) tend to classify color, the sometimes ill-fitting names attached to "red" vegetables become much more understandable.

In the late 1960s, anthropologist Brent Berlin and linguist Paul Kay put forth a theory about how terminology for color develops in languages after finding strong commonalities between 80 different languages. One of their theories was that most languages, when developing terms for color, go through seven different evolutionary stages. In the first stage, most colors are referred to in terms of different shades of black and white. But in the second, red becomes a primary descriptive color. Red, because of its ubiquity as a category, has been used throughout human history to describe colors that, today, we wouldn't truly consider to be red, and you can see that in other somewhat inaccurate color euphemisms that we use today. Natural red hair, for example, is generally more orange in hue, and red wine certainly has a red hue to it but is almost always more purple than scarlet or crimson. Really, "red" is a catch-all term for a loose group of hues, including yellow, orange, pink and purple.

Red onions have also earned their "red" name because their purplish skins have historically been used to make reddish dyes. Research has found that while the dyeing method used for pulling color from onion skins is not necessarily the most ecologically sound (the process uses metal mordants), the resulting dye can leave deep and varied hues in cotton, silk, and a number of other fabrics. And, because it's sourced from food waste, the dye is incredibly cheap. You can see the same dye effect to some extent in other red vegetables; red cabbage can be used as a natural food dye, for example (it works especially well on rice noodles).

But perhaps the simplest explanation for why red onions are called "red" is simply because, well, they sometimes are red. Like all plants, red onions and cabbages are dependent on soil quality and growing conditions for their ultimate appearance. A soil's pH balance can significantly change how "red" an onion appears. In some cases, genetics and artificial selection play a role in the onion's overall coloring. Some seed companies now sell pink permutations of red onions, while other seed strains are prized for their deep purple color.

So whether the onions (or cabbages or grapes) in your grocery store's produce section are red, purple, or some shade in between, you can take comfort knowing that the name isn't wrong, necessarily. Instead, it's just an anachronistic quirk that's carried on into the present time.