People are only just realizing what it means when Coca-Cola bottles have a yellow cap

Coca-Cola rarely breaks tradition from its iconic red packaging, and when it does its usually for a good reason as some people have only just realized after spotting some coke bottles with a yellow cap.

Since its inception in 1886 in Atlanta, Georgia, Coca-Cola has been known for its vibrant and iconic red look.

The bottle's logo designer, Frank Mason Robinson, reportedly came up with the brand's distinctive cursive script and colour palette in a bid to maximise its recognisability.

People have long thought the red coloru came from one of the company's first advertisements, which was staged over Christmas and featured Santa sporting his famous red-and-white get up while holding a bottle of Coke.

Some think the red color was a marketing ploy that involved Santa (Library of Congress/Corbis/VCG via Getty Images)

However, the company said there's actually a logistical reason behind the colour, as more than 130 years ago, the drink was sold in barrels to American drug stores and pharmacies, in the same way alcohol was distributed.

Yet as alcohol was taxed at the time and soft drinks were not, the company decided to paint its barrels bright red to help customs and tax officials differentiate them from barrels of booze.

The shade stuck ever since, but some eagle-eyed customers have noticed new Coca-Cola bottles have been topped with yellow caps.

This is a move which has left people wondering if the colour switch up is a sign that the company is abandoning its century-old tradition.

The red packaging certainly stands out on the shelves (Jeffrey Greenberg/Universal Images Group via Getty Images)

However, some have pointed out on social media that the yellow caps point to something else - that the soda is kosher-approved in time for Passover, a religious holiday celebrated by those who follow Judaism.

The holiday of Pesach (or Passover) is significant for Jewish people as they commemorate those who were enslaved in Egypt and their liberation, spanning a period of seven days.

During the week, various food and drink are prohibited, such as oats, wheat, barley, rice, corn and other common food items, including beer and liquor.

Some bottles have a yellow bottle top (kosherguru/Instagram)

Items that are considered kosher during Passover are those that adhere to the religion's dietary rules.

Regular Coca-Cola beverages do not meet this threshold as the drink contains corn syrup.

However, the company has produced a version of the drink without the prohibited syrup, and have signified its kosher-safe and Passover-ready drink with a bright yellow cap.

Users on Twitter have taken to the social media platform, seemingly astonished that they're only just realizing what the yellow caps mean.

One person said: 'Just learned Coca-Cola does special sodas with yellow caps to indicate they're kosher' while another said the yellow cap 'means it's kosher for Pesach. I just learned about it this year myself'.