You know pencils are yellow, and nothing points to a classy entrance like a red carpet. But do you know how these items got their iconic colors? Here are their back stories.

1. Why do first place winners get blue ribbons?

Knights who were part of France's Order of the Holy Spirit, founded in 1587, wore a special cross on a blue ribbon, or le cordon bleu, around their necks. The French phrase came to be associated with honor, achievement, and a delicious chicken dish. And when passenger ocean liners started to race across the Atlantic in 1830, they did so for the Blue Riband, a coveted prize that didn't actually exist in physical form until 1935. (Once it did, the winners claimed a trophy and a blue pennant they could fly on their ships.) Since then, the pursuit of blue ribbons—by land, by sea, by classroom science fair—has become an American pastime.

2. Why are barbershop poles red and white?

In medieval times, the trusted neighborhood barber didn't just give men a trim and a shave. He also performed tooth extractions, bloodletting, and minor surgery. Thus, the white and red colors on the traditional barbershop pole are said to represent blood and bandages. The addition of blue to the mix on American barbers’ poles is probably an expression of patriotism.

3. Why are pencils yellow?

Pencils were either unpainted or painted a dark color until 1890, when the L. & C. Hardtmuth Company introduced the Koh-i-Noor luxury pencil, named after what was then the largest diamond in the world. The writing utensil's high-quality Chinese graphite was the real selling point, and the company painted the pencil yellow to connote royalty and heroism. The gimmick worked so well that competitors soon started making their own yellow pencils. Sharp thinking!

4. Why do referees wear black and white stripes?

In the early 20th century, refs wore white dress shirts, bow ties, and beret-like hats, which probably made heckling them a little too easy. When a ref named Lloyd Olds got mistaken for a football player and passed the ball in 1920, he decided it was time to change clothes. A year later, he showed up at a game wearing the black and white striped shirt we know—and sometimes mock—today. Fans hated the new look, at least until they realized it really did help distinguish the referee from the players.

5. Why do celebrities walk the red carpet?

Long before movie premieres and snarky fashion commentary, red rugs and carpets were rolled out to welcome royalty and sacred figures. The ancient Greek playwright Aeschylus first mentioned the ritual in the play "Agamemnon," and President James Madison stepped off a riverboat and onto a red carpet in 1821. By 1902, the red carpet was a more inclusive symbol of hospitality for railroad passengers. It was re-associated with royalty—the Hollywood kind—when it debuted at an awards show in 1961.

6. Why are white flags waved to surrender?

The white flag goes as far back as China's Eastern Han dynasty (25-220 CE) and Ancient Rome's Second Battle of Cremona (69 CE). The color was convenient before it was symbolic—white fabric was abundant, easy to see outdoors, and couldn't be mistaken for the colorful banners armies carried when they were ready to fight.

7. Why are baby girls dressed in pink and baby boys dressed in blue?

Gendered baby clothes haven't always been the norm in the U.S. For centuries, baby girls and boys were dressed the same — in cloth diapers and white dresses that probably didn't stay white for long. When pink and blue baby clothes were introduced in the mid-19th century, there weren't strict rules for how to wear them. Some people thought blue clothing looked better on blue-eyed, blonde babies and pink on brown-eyed brunettes. Others suggested that boys looked better in pink, because it was a stronger color.

Clothing manufacturers in the 1940s ultimately decided which colors were for which gender. They started making more dresses in pink and tiny pants in blue. The trend died down in the '70s and came back with a frilly-or-football-printed vengeance during the '80s once ultrasounds allowed expectant parents to learn their children’s genders before the babies made delivery room debuts.

8. Why are fire hydrants lots of different colors?

Good eye! The association of red with fire hydrants goes back to the early fireplug, a well of water plugged with a piece of redwood. But there are plenty of hydrants out there that aren't red. That's because they’re color coded to give firefighters details about their water supply. For example, hydrants using public water systems are yellow with various colored tops and caps to indicate how many gallons per minute (GPM) of water they have available. The tops and caps of hydrants supplying below 500 GPM are red, 500-999 GPM are orange, 1000-1499 GPM are green, and 1500 GPM or more are blue. (Don't worry. There won't be a test.) Red hydrants use a private water system, the rare purple hydrant supplies non-potable water, and a black fire hydrant won't save anyone because it's inoperable.

9. Why are barns painted red?

In the 18th century, farmers were trying to break the mold ... literally. They covered their barns' wood with a mixture of linseed oil, milk, and lime that turned the wood burnt orange. When that still didn't stop mold, farmers added rust, or ferrous oxide, to the mix. It helped tremendously, while also turning the wood that lovely shade of red known as falu. Then when mass-produced paints were made available in the late 19th century, red just happened to be the least expensive color available. Now the color chosen out of practicality and frugality is a charming tradition.

10. Why do doctors wear white coats?

You know what they say—dress for success. In the 19th century, most physicians tended the sick while wearing street clothes. With quite a few quacks running around at the same time, this business casual approach didn’t feel very official. Doctors started wearing white lab coats in the early 1900s to give the profession an image makeover. The coats bolstered their reputations by connoting scientific authority and sterility. (Medical innovation and more thorough training eventually helped, too.) Ironically, some modern hospitals ban white coats, because they spread germs and cause anxiety in patients.

11. Why are scrubs usually blue or green?

First came street clothes, then came hospital whites. But by the middle of the 20th century, doctors and nurses were tired of having to throw out uniforms once they got the inevitable stains that come with practicing medicine. Hospitals switched to blue or green scrubs that were easier to clean. Another advantage of colored uniforms: they make looking at the inside of a human body easier on surgeons' eyes, since blue and green are opposite red on the color wheel.

12. Why are most fast food logos red or yellow?

It's no coincidence. According to color psychology, warm reds and yellows subconsciously stimulate the appetite and trigger excitement and positivity. Fast food places use these colors on everything from logos to trays to décor to entice customers to happily gulp down food without hanging out too long. Cool colors, on the other hand, tend to suppress the appetite and slow everything down. The color of food packaging also affects how much people eat. White plates, boxes, and wrappings are said to encourage mindless overeating, even when a person is already full.

13. Why are basketballs orange?

In 1957, regulation basketballs were either tan or, if both teams agreed to it, yellow. Butler University’s basketball coach felt an orange ball would be easier for both players and spectators to see, and the orange ball made a successful test run in the 1958 college championships in Louisville. Orange was added to the list of color options a year later and is now the standard.

14. Why are tennis balls yellow?

Same story, different sport. The governing bodies of tennis actually approve both white and yellow balls. Because it was easier to see on color TV, the fluorescent yellow ball quickly became the norm after it was introduced in 1972.

15. Why does a red traffic light mean stop and a green one mean go?

The traffic light color scheme goes back to England in 1841, when the Liverpool and Manchester Railway—the world's first twin-track inter-urban passenger railway—decided to step up its safety game with colored flags, semaphores, and lights. The scheme followed that of other industrial equipment at the time. Red was a sign of danger, while green meant proceed with caution.