There are many parts of the world where, for much of human history, food was likely a dull visual affair. Take Tuscany, the culinarily renowned region of Italy that the writer Bill Buford muses on in his book about cooking, Heat. He details a near-monochrome local cuisine that has been passed down through the generations: Crostini with chicken-liver paté? Brown. Beans? Brown. Roasted pork, veal, sausage? Brown, brown, brown. Even the vegetables: Buford classifies Tuscan artichokes and olives as "green-brown," and more amusingly, the porcini mushrooms as "brown-brown."

Over the past 150 years, food companies and marketers in other parts of the world have taken eating in a more visually thrilling (if a little disorienting) direction. They have used dyes to alter mass-produced foods—sometimes to make them less “natural”-looking (see: cakes with bright-blue icing), sometimes to make them more “natural”-looking (pickles made greener to fit with consumers’ expectations). Both intentions are, upon further inspection, sort of strange. The first one is odd because it’s not entirely clear, even to researchers, why anything with some abnormally bright colors would be appetizing at all, given that when, say, the color blue appears in nature, it’s often a sign of spoilage or poison. And the second is a paradox: How could a food be made to look “more natural” by virtue of artificial additives?

These sorts of tensions fascinate Ai Hisano, who’s currently a fellow in business history at Harvard Business School. Hisano is a historian by training, and when it comes to the colors of mass-produced foods, she directs her attention toward the period from roughly 1870 to 1940, when artificial coloring went from occasional gimmick to food-marketing norm.

Starting in early 19th century, it became increasingly more common for businesses to manipulate foods to give them a standardized, recognizable appearance: Bakers would whiten bread with chalk, dairy farmers would add a lead compound to milk to make it seem thicker, and, later in the century, meatpackers began to inject red dye into cuts to make them look fresher. (As unhealthy as these “ingredients” sound, the bigger risk was that they were masking mold or spoilage that could sicken or kill.) But one thing that made the revolution Hisano documents possible was the discovery, in the 1850s, of a vivid magenta dye made from the liquid left over after processing coal—a repulsive-sounding (but usually safe) additive that could be synthesized on the scale necessary for mass-produced foods.

Nowadays, manipulating foods’ colors is the norm (and much safer), and even a consumer expectation. Grocery stores know that only pristine-looking apples sell—hence the shiny wax coating that growers apply before shipping. Never mind that more “natural” apples, the ones straight from the orchard, vary in color and often have dents and bruises.

I recently talked to Hisano about the history of how marketers control the colors of foods, how what’s considered natural (and acceptable to eat) has shifted over time, and what to make of consumers’ recent pushback against synthetic additives. The conversation that follows has been edited for length and clarity.

Pinsker: Recently a lot of companies have started using natural dyes instead of artificial ones for their products, like M&M’s and Kraft Mac & Cheese, and they’ve done this because there’s a sense that consumers want their food to be made up of things they recognize. How does your understanding of the history of food coloring change how you view this trend?

Hisano: I think it goes back to the era—the 1870s and 1880s and the early 20th century—when the increasing use of food dye normalized the artificial coloring of food. That’s the beginning. Then, one of the biggest changes among consumers’ attitudes toward the use of colors happened in the 1960s and ’70s, with the counterculture movement and also a kind of back-to-nature movement, when consumers responded to the use of chemicals, not only in food coloring, but also things like DDT and other chemicals in agriculture and food processing. I think that the ’60s and the ’70s were when consumer movements against chemicals really accelerated.

But, even as that’s happening, artificial coloring is still considered normal. Even today’s conscious consumers mostly aren’t asking for companies not to use dyes at all; they are just asking to substitute synthetic dyes with natural ones. They probably don't want foods without any colors, which can look kind of ugly.

This reminds me of something that happened with Starbucks. Starbucks was using what is called a cochineal dye, which is a natural dye derived from insects, to color its strawberry Frappuccinos. It’s a natural dye—it’s not synthetic—but many American consumers thought it was gross to use insects for dyeing a milkshake. So they petitioned against using those dyes, and Starbucks started using a tomato-based dye instead. Consumers were happy with that. But tomato-based dye for strawberry-flavored drinks is not really natural—it’s just assumed that it’s normal to color food, as long as the dyes or the ingredients are things that consumers consider safe or natural.

Joe Pinsker: Have humans always been manipulating the color of their food? When did synthetic dyes start to be widely used?

Ai Hisano: It wasn’t necessarily mass-produced in factories like some other products, but butter was one of the earliest food products that was colored using synthetic dyes. The artificial coloring of butter has a long history, going back at least to the 14th century—European farmers back then colored butter with carrot juice and annatto, which is a dye made from tree seeds. They did this to make it the same color year-round, because it is naturally yellower in the summer, when the grass that cows eat has more pigment in it.

So in the mid- to late 19th century American farmers began coloring butter by using food dyes produced and supplied by dye manufacturers, rather than making the dyes themselves. The dyes, or synthetic dyes, produced by manufacturers were more standardized and stable, so dairy farmers could color butter a more uniform yellow. Before the late 19th century, butter had been colored, so it’s not as if the color of butter all of a sudden became yellow year-round. But the use of synthetic dyes was a change, and dairy farmers did this to some types of cheese as well, like cheddar.

Pinsker: As foods’ colors got standardized, did consumers start to make different assumptions about how their food was made?

Hisano: Well, I haven’t studied how consumers came to understand food production. But I think in several instances, as producers came to market colored fruits or vegetables or other foods, consumers came to expect any produce to be uniform in shape and appearance, all year, without seasonality.

I think that attitude changed over time, and especially these days, people are more suspicious about the use of chemicals in agriculture or even processed foods. Those kinds of changes are reflected by the rise of Whole Foods and organic markets, which charge premium prices and make the claim that they don't use chemicals. I think that consumers’ attitudes toward how food should look have changed—having foods look uniform and consistent could be a downside rather than an advantage for food companies and food producers.

Pinsker: I want to talk more about the earlier days of dyeing foods, back when safety was a concern—lead compounds were being used to make milk creamier, and dyes used in some candies turned out to be poisonous. Sometimes, people actually died from eating them. How could dyes get so popular while also being so dangerous?

Hisano: As you said, there were many instances when dyes, especially red dyes, killed people and many people became sick. I assume many consumers in the early 20th century were frightened by those bright-red foods. But one reason consumers liked them is because they were excited about these colors they had never seen before. And one reason they thought they were safe was because of the Pure Food and Drug Act in 1906, when the government endorsed certain dyes as safe, even though some of them turned out to be unsafe. Food companies were advertising that they were using approved dyes for their foods, so consumers were seeing that. I think that the government’s endorsement helped companies to market dyed foods as safe, but as you said, there were real dangers.

Pinsker: You grew up in Japan and studied at the University of Tokyo. When you started living in the U.S., what impressions did you have about the colors of American foods?

Hisano: When I first came to the United States, the very bright, vivid colors of cake frosting and cupcakes were really shocking to me. It was more than 10 years ago. And still I don't quite understand why that brightness makes people hungry. Maybe it’s primarily for eye appeal rather than for taste.

Pinsker: What era did that come from? When did it become popular to make bright blue cakes?

Hisano: That goes back to the 19th century, as far as I know. In the late 19th and early 20th century, companies started selling food coloring for household use, and many cookbooks and women’s magazines introduced recipes for “dainty dishes”—visually appealing foods that had been heavily decorated. These included not only cakes but also some other desserts and sometimes sandwiches, and in a way, making dainty dishes was a way of displaying femininity and women's creativity. And this was mainly for upper- and upper-middle-class women, because it was still expensive to make colorful dishes. After the 1920s, the introduction of cheaper dyes and Jell-O made it easier and cheaper for many women to make colorful dishes.

Pinsker: Can you tell me about the book you’re working on?

Hisano: I’m writing a book specifically about the color of foods in the U.S. Many historians have studied how businesses changed the way people thought about their surrounding world by, for example, looking at the history of railroads, electricity, and the telegraph—technologies changed the concepts of time and space. But this was also a time when people’s sensory experience changed fundamentally, and that hasn’t been studied as much. In the mid- to late 19th century, companies began developing technology that could measure and define sensory perceptions—things that are thought of as subjective and intangible—by assigning numerical values to different colors and analyzing scents based on their chemical components. The book I’m working on now is about the color of foods, but this is what it’s about more broadly.