Culture

What the colours on food packaging are really doing

Painting of a pile of red wild strawberries on a stone ledge against a dark background

Painting of a small heap of green gooseberries on a stone ledge against a dark background

Botanical plate of the cacao plant with leaves, flowers, an open pod and purple beans

RAYGUN - cadmium red, high grade professional acrylic paint, by Stuart Semple 100ml Stuart Semple

HAPPY - cadmium yellow, high grade professional acrylic paint, by Stuart Semple 100ml Stuart Semple

Supermarket shelves run on colour folklore. Some of it holds up in the lab, some of it does not, and one shade of purple ended up in the Court of Appeal.

Green and the health halo

Walk down any cereal aisle and the packaging sorts itself into a colour code that nobody ever wrote down. Green boxes suggest wholesome. Red and yellow suggest a treat. Pale, quiet colours suggest something sensible. Most shoppers absorb this without thinking about it, and that is the point. The interesting question is how much of the code actually works on people, and how much is design folklore repeated until it sounded like science.

Green has the best evidence behind it. In 2013 Jonathon Schuldt, a communication researcher at Cornell University, published a study in the journal Health Communication with the blunt title "Does Green Mean Healthy?" In the first experiment, 93 students imagined they were hungry at a supermarket checkout and were shown a sweet bar carrying either a red or a green calorie label. The calorie count was identical. The students still rated the green-labelled bar as healthier. A second, smaller online study found that people who cared most about healthy eating were the ones most swayed by the green label.¹ Schuldt's conclusion was that the colour and design of a label "may deserve as much attention as the nutritional information" printed on it.¹ He noted that big confectionery brands, Snickers among them, were already using green calorie flags.¹ A green box tells you nothing about what is inside it, but it seems to lower the guard of exactly the people who are trying hardest to read the box properly.

Red, yellow and appetite

The idea that red makes you hungry is repeated in almost every article on fast food branding, usually with McDonald's red and yellow as the example. The research is less tidy than the folklore. In 2016 Francesco Foroni, Giulio Pergola and Raffaella Rumiati at SISSA, the International School for Advanced Studies in Trieste, analysed the colour content of food photographs and found that redder images were linked to higher arousal ratings, while greener ones were linked to lower arousal and lower estimates of calories. The pattern held for cooked and processed foods as well as raw ones, and it did not appear for pictures of things that were not food.² Their explanation was evolutionary. In fruit and vegetables, Foroni said, "color is a good predictor of calories", so a primate eye that favours red has a reason to.²

That is a finding about the colour of food, though, not the colour of the box. When Carina Schlintl and Anne Schienle at the University of Graz recoloured images of sweet foods for a 2020 study in Frontiers in Psychology, tinting them red actually reduced how much the 448 women taking part wanted to eat them, and the authors describe earlier evidence on red and appetite as mixed.³ Blue tinting reduced wanting too, which fits the long-standing view that blue food looks wrong to us because almost nothing we eat is blue.³ So the safest version of the claim is narrow. Red food often reads as rich and ripe. Whether a red logo does the same job for a burger is something marketers assert far more confidently than the studies do.

Colours that stand for a brand

Some packaging colours have little to do with psychology and everything to do with habit. Heinz baked beans have sat in a turquoise label with a black logo for so long that when the company relaunched the range in 2008, keeping the turquoise was part of the announcement.⁴ Nobody chooses turquoise to make beans look tasty. It works because shoppers have spent decades learning to find that exact shade on a shelf. Carlos Velasco and Charles Spence, who study multisensory packaging, make a related point: colour is one of the main ways people identify a product, and a colour that matches the flavour, such as burgundy for barbecue crisps, helps shoppers find it faster.⁵

Once a colour does that much work, companies want to own it. Cadbury has wrapped its chocolate in purple for around a century, and in October 2004 it applied to register a specific shade, Pantone 2685C, as a trade mark for chocolate packaging. Nestlé opposed it. The Intellectual Property Office and then the High Court sided with Cadbury, but in October 2013 the Court of Appeal overturned the registration.⁶ The problem was the wording. Cadbury had described the purple as the "predominant" colour of its packaging without defining what predominant meant, and Sir John Mummery found the application "lacking in specificity, clarity and precision", adding that it would give Cadbury an unfair advantage over its rivals.⁶ A colour can carry a brand's whole identity on a shelf, and English law still decided that a loosely described one could not be fenced off for a single company.

For anyone who has followed the arguments over who gets to use a colour, from Anish Kapoor's exclusive rights to Vantablack to Stuart Semple's PINK, the supermarket is a useful reminder that these fights are not confined to the art world. They happen in the biscuit aisle too, and the stakes there are measured in market share.