There are a lot of countries that are sharing the same language. Sometimes, it's exactly the same, but sometimes there are accents, word changes, spellings changes, complete new words or forgotten words between two countries. Today, for example, I, a Dutch-speaking person from Belgium, was talking to zDutchie, a Dutch-speaking person from the Netherlands, and I used a word she had never heard before. (Gosh that was a long sentence)
We then found out that it was a word that only Belgian people use. This is a relatable situation. People from Great Britain most of the time to always use 'Colour' instead of 'Color', whilst people from America most of the time to always use 'Color' instead of 'Colour'. Both are individually correct.