Color and colour are different spellings of the same word. Color is the preferred spelling in American English, and colour is preferred in most other varieties of English.
Examples
For example, these American publications use color:
The “it” color of the moment is a visual pick-me-up. [Seattle Times]
They are very large and multicolored, often having two or three colors in different shades. [Auburn Citizen]
In some cases, OLED creates better color contrast and uses less power. [Wall Street Journal]
And these non-U.S. publications use colour:
My daughter has impaired colour vision, mostly affecting the colour red. [Sydney Morning Herald]
Special decor touches of colour, texture and whimsy can bring heart-thumping feelings all year long. [Metro]
Woman returned shelter dog because its colour clashed with her curtains [Mirror]
