Which is correct color or color?

Both color and colour are correct, the difference is regional spelling based on American English versus British English. Color is the standard spelling in American English, used in the United States, and it is the preferred spelling in American dictionaries like Merriam-Webster. Colour is the standard spelling in British English, used in the United Kingdom, Ireland, Australia, New Zealand, Canada, and other Commonwealth countries, and is the preferred spelling in the Oxford English Dictionary. Both words mean exactly the same thing and are pronounced the same. The difference originated from historical spelling reforms. In the early 19th century, American lexicographer Noah Webster promoted simplified spellings to differentiate American English from British English, dropping the u from many words ending in our, such as colour to color, flavour to flavor, honour to honor, and labour to labor. British English retained the French-influenced our spelling. So which is correct depends on your audience and style guide. If you are writing for an American audience or using American style guides like AP or Chicago, use color. If you are writing for a British, Canadian, or Australian audience, use colour. Both are correct within their respective systems.