We often do not pay attention to the colors of some everyday things. However, we would quickly notice that something is wrong if we find it in a different color. For example, a blue school bus. Or a green plane. Or a car with red tires. Or brown traffic lights.
We unconsciously expect aircraft to be white, car tires black and school buses yellow. These things often have these colors for some reason. Sometimes it's all about practicality. In other cases, it's about some crazy events in the story.
10 Why traffic lights are red, yellow and green
The traffic light was invented for trains. At that time, it only had two colors: red for stop and white for go. A green light was added later to signify caution. So it was red for hold, green for caution and white for on the way.
However, the white light soon proved problematic, as the train drivers often considered it a distant star or another light. Train companies noticed this and replaced the white light with green. So it was red for stop and green for go. The road traffic supervisor took the traffic lights as vehicles drove by.
They did, however, contain a yellow light to signify caution. Yellow was selected because it has a shorter wavelength than red, but a longer wavelength than green. The difference in wavelengths is the reason why red is most visible from a distance. Yellow is less visible than red, but more visible than green. 
9 Why taxis are yellow
Yellow is considered the actual color of taxis, though they may appear in different shades depending on local regulations. While some states, such as New York, require taxis to be exclusively yellow, others have prescribed a different color. Why? Well! This is thanks to John Hertz, who eventually developed the Hertz rental car company.
Taxis were not exclusively yellow decades ago. In fact, the first New York taxis appeared in different colors, especially in red and green. This changed after John Hertz built his taxi business in Chicago in 1915. Hertz funded research to determine the most visible color for a motor vehicle.
The study found that yellow is the one. That's how the yellow taxi was born. Other taxi companies soon followed Hertz's strategy and began to color their taxis yellow. The color became so common that states like New York changed their laws to require all taxis to be painted yellow.
Interestingly, Hertz was not the first to paint his taxis yellow. In 1909, Albert was Rockwell. In 1912, Rockwell even named his taxi company Yellow Taxicab Co. However, he had no practical reason to use yellow and chose the color only because his wife liked it. 
8 Why school buses are yellow with white tips and black letters
Under US law, all school buses must be yellow. The law even requires the type of yellow, which is aptly called the "school bus yellow".
School bus yellow is a real color named after the school bus. It's actually a mix of yellow and orange. Before the law, these vehicles were painted in a yellow shade that looked like lemons. The Yellow School Bus was selected during a 1939 conference to determine the characteristics of US school buses.
The conference participants agreed on the color yellow, as this is the most visible color for a vehicle. Studies have shown that we can spot a yellow object, even if it is not directly in our view. The participants called it the "national school bus chrome". Later, however, it was renamed "Schulbus-Gelb". 
Yellow school buses often have black letters as black is the most distinctive color can be used against a yellow background. The top of school buses is often white (which is considered a lack of color in some contexts) because they reflect sunlight better than other colors. Dark hues absorb sunlight and cause heat in the buses.
7 Why Fire Trucks Are Red
Earlier, red was the de facto color for fire engines. Today, however, they are available in different colors, depending on local regulations and the fire department. The reason why fire engines used to be red is unclear and the explanations are even contradictory.
Some sources claim that the first fire engines were red because they were the cheapest paint. The fire departments were at that time with unpaid volunteers and had not much money left. So they painted their vehicles with the cheapest paint they could get. 
A second and contradictory theory says that the first red fire truck was the result of a competition between the firefighting divisions. These groups were allegedly occupied by volunteers at the time. However, individual fire departments wanted to stand out. So they searched for the most expensive color they could get – which was red.
A third theory states that early fire engines were painted red because firefighters wanted their vehicles to be visible to other road users. That's why the firefighters opted for the color red, which was very visible and unique at a time when most vehicles were black. However, this theory is controversial, as colors such as yellow and lime green offer better visibility than red.
6 Why crosswalks are black and white
In the late 1940s, the British government launched a nationwide experiment to determine the best colors for marking pedestrian crossings. The experiments became a necessity after a series of accidents involving pedestrians and motorists.
At that time, Britain experienced an increase in motor vehicle ownership. This became a problem as motorists often mowed across pedestrians who were not used to sharing the streets with cars. The government has created pedestrian crossings, but they have done little to reduce accidents. This was because the intersections were marked with metal pins that were almost invisible to the drivers. 
The government later decided to switch to colored markers, and launched the experiment to determine the best colors of the streets. They found that black and white was the most visible pattern. Motorists could see it from a greater distance than other colors. At the same time, the crossing pedestrians became visible to the drivers because they stood out from the background.
The crosswalk got its name only after then-deputy Jim Callaghan visited a black-white pedestrian crossing during the experiment, noting that it resembled crosswalks. The first official zebra crossing appeared on October 31, 1951.
5 Why hydrants were red
In the past, red was the actual color of the hydrant. However, they nowadays appear in a variety of colors. While many fire hydrants are coated with a random light hue to make them visible to passing pedestrians, the paint jobs are not always arbitrary.
The paint could be used to indicate the source of water for the hydrant. In this case, a yellow coating indicates that the hydrant is connected to the public water system, while a purple coating indicates that it is connected to a lake or pond. Alternatively, the paint job could be an indicator of the liters of water the hydrant can deliver per minute.
The strongest hydrants are painted blue. They can deliver at least 5,680 liters of water per minute. Green hydrants deliver 3,785 to 5,680 liters of water per minute. Orange hydrants deliver 1,890-3,785 liters of water per minute, and red hydrants deliver less than 1,890 liters of water per minute. 
4 Why aircraft are white
Civil aircraft are almost exclusively white. There are mutliple reasons for this. One is the cost. Colors are expensive. A regular painting costs between 50,000 and 200,000 US dollars. This could be too expensive for a low-cost airline purchasing a used aircraft from a larger airline. White paint also saves money because it is not as maintenance intensive as other colors.
White is also popular with airlines because it reflects sunlight from the plane. A darker color would absorb the heat and make the interior of the aircraft warmer. At the same time, white reduces the risk of radiation and protects important parts of the aircraft, such as the nose cone, where the radar is often located. 
A white finish allows maintenance personnel to detect cracks, bumps and leaks easily. It also reduces the possibility of air raids as birds can see white better. After all, white aircraft parts are easier to detect on the ground or in the sea after a plane crash.
3 Why Toilet Paper Is White
Toilet paper is almost always white because it was bleached. This is the same reason why the normal paper we write on is white. Normal and toilet paper would be brownish-gray if not bleached.
We understand that plain paper is bleached white, so we can see everything on it clearly. But why is that done with toilet paper? Bleaching costs money and makes toilet paper more expensive. It is also a unique product. So why bother?
Now! This happens for two reasons. First, manufacturers bleach paper to remove lignin. Lignin makes trees stiff – and it does the same thing with paper. Nobody wants stiff toilet paper. So it's bleached.
A second reason is that we consider everything that is white clean. Therefore, manufacturers who make toilet paper from recycled paper bleach it white even though it does not contain lignin. In addition, the unbleached product would appear in different colors and shades because the paper comes from different sources. 
2 Why footballs were reddish brown and then black and white
] The first leather soccer balls were reddish brown because natural leather has this color. Therefore, the manufacturers often left the color unchanged. The reddish brown football was used for the World Cup until it was replaced in 1970 by a black and white.
FIFA allowed Adidas to design the black-and-white ball, as the World Cup was getting televised at the time. And it would have been difficult for viewers to spot a colored football on their black and white televisions. Adidas used a mix of black and white because the black dots allowed viewers to determine the direction of the ball on their black and white televisions. 
Adidas called this ball the "Telstar". However, some sources claim that the ball was actually named after the Telstar satellite that broadcast World Cup games around the world.
1 Why Tires Used To Be White, but now black
Tires used to be white because the natural color of rubber is white. Unfortunately, these tires were not very durable. They carried quickly, reducing handling and cracking when hit by the sun's ultraviolet rays. Tire manufacturers solved this problem by adding carbon black around 1917.
Soot immediately solved the multitude of problems associated with white tires. For this reason, black tires hold tens of thousands of miles while white tires barely travel 8,000 kilometers before they had to be replaced. However, soot – as the name suggests – made the tires black.