Add plural "colourations" / "colorations"

[Dimitri Papadopoulos Orfanos]

Only the plural is missing. Yet plural makes sense, for example "lepidopterans with different colourations".

From the Google Books Ngram database:

• https://books.google.com/ngrams/graph?content=coloration%2Ccolourations%2Ccoloration%2Ccolorations&year_start=1800&year_end=2019&corpus=en-2019
• http://app.aspell.net/lookup-freq?words=coloration%0D%0Acolorations%0D%0Acolouration%0D%0Acolourations;also=similar;parm=full