I had an anonymous comment on my i-cord trim. Since I don't know where to reply I have to do it here. I-cord is not sewn on, it's all knitting. And you can learn how to do it HERE. Though I think I did it a little bit differently.
You make a trim with it by knitting the last stitch of every row together (and twisted) with a stitch along the trim. For my purple and lime sweater I did this:
I picked up a full row in lime along the neckline, then cast on an extra three stitches to make the i-cord from.
Knit two stitches
Knit next two together through backloop.
Put three stitches back onto left needle.