Hmmm...when it comes to trends, I don't think colors really come in and then go out. There may be colors that are more prominent from season to season. However, I don't think anyone would look "dated" wearing green assessories, unless we are talking about bright neon green.
Starting last year, kelly green has definitely been trendy.
Now, a trend is different than a fad - a fad lasts for a short period of time, a trend usually lasts 3-5 years. I know we all use the word trend when the word fad would be more appropriate (especially when it comes to quickly changing fashion), but kelly green falls into the longer time period of a trend in the classic sense. The late eighties and early nineties saw forest green as a trend in greens - for the past decade this shade has been considered dated, but is starting to make a comeback.
So, even though "green" as a color is not trendy, certain shades can be.
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"Fashion can be bought. Style one must possess." ~ Edna Woolman Chase