When I was knitting the arms, I would carry the yarn if I was only skipping over two rows, otherwise, I would cut the yarn.  There were dozens of ends along the seam where I was making color changes and cutting the yarn.

When it came time to do the finishing for the arms, I looked at a ton of different ways to weave in ends.  I really liked what is basically duplicate stitch on the back.  See how I'm weaving in the ends below?  It's a beautiful thing!

These photos show me weaving in the light purple yarn.

This shows both the end of the dark yarn and the beginning of the light yarn woven in on either side of the seam.

After weaving in 6 ends (three side-by-side sets), I tried the sweater on and discovered that weaving in so many ends so close together resulted in a stiff, lumpy fabric along the underside of my sweater arm.  The result was very unattractive and uncomfortable.

So I unwove all those ends.  And I stared at them.  And all I wanted to do is just cut them all off.

So I did ... after some hand sewing. :)

I threaded the blue yarn up the middle of the seam as a guide from the right-side of the fabric because it was easy to tell where the "seam" was from that side.  

Then I turned the sleeve inside out.  With all the carried and cut ends, the seam was less obvious.  The blue yarn was a super helpful guide.

One stitch to the left and one stitch to the right, I sewed up along the "seam".  When I came to a yarn end, I went through the yarn, then around the yarn, then pulled the thread tightly, and then I knotted the thread.  

I had to go up both on the left and right because when I started a new yarn, the end was on the left and when I broke yarn, the end was on the right.

Here's another shot of my sewing with the ends snipped.  I'm going to leave them just like that.

The last bit of finishing for the sleeves was to sew up the "seam" from the outside for extra security.

The next time I do color changes in a tube like this, I want to carry the yarn along the seam and just twist them every row.  This sweater only has 3 colors, so there would only be 2 yarns being carried at any given time, which wouldn't be too bulky.

Does it freak you out that I hand-sewed the seam and cut the ends short?

SPOILER ALERT: I'm already done with this sweater, but I still have a couple of posts left before I do the big reveal.  I only admit this because I've worn the sweater 3 times already *and* machine washed & partially machine dried it and the "seam" is superduper awesome.  So, no need to worry that the whole thing is just going to fall apart as I wear it.  This totally worked, as janky as it is. :)