My Dennis the Menace stripey jumper has been sitting on the side, while I was working out how to match the stripes across the sleeves from the body. I've read several times in 
Part One: Designing and knitting the sleeve head or cap - the part of the sleeve that fits over your shoulder.
Part Two: Completing the top-down sleeve using the magic loop method.
These were good starter videos, but didn't address matching the stripes on the sleeve with those on the body.
Instead, I started at the shoulder seam at the top of the sleeve and picked up three stitches (one on the seam and one either side), then I started knitting short rows, back and forth, knit one way and purl the other, picking up another stitch at the end of each row until I had completed the top stripe.
The next (blue) stripe was worked slightly differently. For this, and each subsequent, stripe, I picked up all the stitches at the edge of that stripe on the body, knitted across the "live" stitches already on the needle from the previous stripe, and then picked up all the stitches on the stripe on the edge of the opposite side.
Then I purled back up those last picked up stitches, purled across the live stitches, and purled one of the picked up stitches on the other edge, wrapped the next stitch and turned, knitted across the live stitches to the other side, knitted one from the picked up stitches, wrapped and turned.
From here, I continued back and forth, knitting one way and purling the other, picking up another stitch from each side each time. By the time I had completed the stripe (twenty rows) all the stitches had been incorporated into the stripe. Just by luck, I had chosen twenty rows for the depth of each stripe: it made it very easy to calaculate when to pick up stitches (and also to check when I was done with each stripe). The very top stripe was ten rows.
In the video, the sleeve is completed using circular knitting. Again, because of wanting to match the stripes, I decided to knit the remainder of the sleeves using flat, back and forth, knitting, creating a seam at the underarm. I had 90 stitches when the sleeve head was completed, which I wanted to reduce to about 50 at the wrist. I calculated that it would take 80 rows to finish the sleeve at the length I wanted. I decided to decrease one stitch either end every four rows for 72 rows, then finish with a k2:p2 rib (similar to the body).
I used crochet, matching stitches from each side of the sleeve, slipping through the yarn and then slip stitching the previous loop. This was very easy and fast to do and matched the stripes perfectly. On the first arm, I pulled the crochet stitches a little tight (the jersey is definitely a sloppy joe arrangement). It doesn't show when you are wearing it, but I will probably re-do that arm seam.
I'm going to re-do the collar, and now that the main body of the jersey is complete, I will probably complete it in the blue. Since I tried the collar, some people have sent me some other suggestions, so I will start again. One thing I hadn't realised is how deep the collar needs to be - about four inches (10 cms).
I have six buttons and eight buttonholes ... so a trip to town to find two more buttons ... and then there's just sewing in the ends. I think that might be a soothing job for when I'm watching tv or maybe a knitting group where everyone is chatting as well.
Previous posts about making this jersey
Dennis the Menace Stripes
Stripey Jersey: 3-needle shoulder seam bind off
Swatchtaping