Intarsia is “normally” done while knitting flat. For an instruction on intarsia see this nice post over at the Purl bee on the subject. It is possible to use intarsia for round objects without seeming afterwards and yes there is a reason I didn’t say knitting in the round. There are at least 2 methods (or 3 depending on how you look at things) out there on the interwebs, and I would not be surprised to find more.
The first that caught my attention was described by Moth heaven. This method is worked in the round, with the added colour section worked back and forth two rows at a time, and then slipped as you work the second row with the main colour. Below is a few charts that shows how this is performed. The numbers represent the order in which to knit the stitches and s is for slipping a stitch.
I understand the principle and I can execute it but the tension is all over the place. I just couldn’t get it too look right.
There are also methods for working the intarsia part flat. Either using wrap & turn (w&t) or yarn overs, which to me at least seems to be the same thing – wrapping stitch or needle and subsequently sealing the joint as you go. Below is again a chart to demonstrate the order of working a tube back and forth by using wrap & turn and working the wrap with the stitch on the next row.
Both these created the same end result. At least if you can manage to keep a steady tension. For me the second method was easier to use to produce a nice result from the get-go. It’s what I’m using for my SYTYCK project.