But the restaurant managers have another trick up their collective sleeve. As well as using yellow to evoke happy feelings and ensure their signs can be seen from a distance, many of them also employ a little-known trick called the ‘ketchup and mustard theory’.

This theory refers to the repetitive use of red as well as yellow, as we can see in so many fast food signs. The yellow ‘M’ for Mcdonalds sits on a red background, while the yellow buns enclose red lettering used to spell out Burger King. Plus, the roof above the Pizza Hut logo is symbolised with a bright red splash of colour.

According to the theory, the combination of these colours makes people want to stop what they’re doing and eat. The red colour makes people feel comforted and hungry, while the yellow makes people feel happy and excited – which is just the way you want to be feeling when you’re heading to the counter to order a box of McNuggets. Thanks, restaurant signs.

stylist.co.uk has had a yellow makeover on 15 August, to celebrate our Yellow Issue and pay homage to the colour of the season. Read more about the most playful shade of all here.

Main image: Unsplash

This is why fast food restaurant logos are yellow