Both forms are correct. Colour and color are both correct spellings in English; the former is a British spelling and the latter is an American one. The difference in spelling comes from Noah Webster’s dictionary published in 1828, which introduced new, American ways of spelling some English words. It was to simplify and standardize spelling in American English. Among others, -our endings in words were changed to -or, according to the pronunciation (colourcolor; honourhonor, etc).

Correct spelling


Correct spelling, this spelling is preferred in all other main varieties of English.

Correct spelling


Correct spelling, this spelling is preferred in American English.

Definition of color/colour:
noun, the property of an object, which is created by the way it reflects light, that produces different visual sensations
This jumper is very nice, but the colour doesn’t suit you.
I would pick different colors for the walls, these are way too dark.