There are sometimes disputes over the spelling "coloration" in British English.

Both the spelling "coloration" and "colouration" can be found in British English. However, searches as of January 2019 showed that "coloration" is the more common. Google Scholar (a somewhat better indicator of thoughtful usage than Google) showed a ratio of about 9:1 for "coloration" vs. "colouration", whereas "color" was only about 10% more common than "colour". If we assume that no-one uses "colouration" + "color", some algebra suggests that to get these ratios, then of these sources roughly:

  • 52% would use "color" + "coloration"
  • 38% would use "colour" + "coloration"
  • 10% would use "colour" + "colouration"

This gives about a 4:1 ratio of "coloration" to "colouration" in British English. A Google ngram applied to British English confirms this, with "coloration" at least 4 times as common as "colouration".

So I conclude:

  • There is clear evidence that "coloration" is the most common spelling in those varieties of English that use the spelling "colour".
  • Where there are choices within an ENGVAR, MOS:COMMONALITY encourages us to choose the one with greatest commonality. Hence we should prefer "coloration" in British English.