Necessity was the mother of invention for this technique. The body of this sweater was made with a wonderful mohair, silk and linen blend. As the knitting progressed, the yarn 'said' (in that way yarn talks to knitters) that although soft, it wasn't a good choice for the collar.
The color of the body was a varigated grey with a definite blue tinge and surprisingly difficult to match. My husband got involved (after all, it was his sweater) and selected the darker of the two greys used in the banding. It was a good choice, given what was available, but it wasn't quite right. By happy accident, I stumbled upon the perfect grey in a sale bin.
A 'political' problem arose. How could I disregard my husband's color choice? Especially, since both solid color yarns, used together, worked well. Both needed to be part of the collar, cuffs and bottom band. But, how? If I hadn't knitted the body with a rectangular shawl collar in mind, this sweater would have ended up with Fair Isle, corrugated, ribbing. That was a good, traditional, solution with two drawbacks: it didn't have the elasticity of regular ribbing and it wasn't reversible.
The yarns and sweater body 'stewed' in the knitting basket as I mulled over options. I'd double-knitted before, but never with textured stitches. In fact, I'd never seen it done - but, why not? In the finished sweater, cuffs and ribbing are double-knitted in two-color 3 x 2 ribbing and the collar is double-knitted using the basketweave pattern of the body. On the collar, a band of the medium grey made the transition from the body to an edging of the two-color border.
The result? The proof was in the wearing! It was warm and comfortable. It balanced the characteristics many men especially seem to like: plain, but with some 'interest.' The double knitting is warm, elastic and reversible. Definitely a winning technique.