Purling on circular needle with 2 colors

I am knitting a Christmas stocking with 2 colors on a circular needle. To make a braided edge it requires me to purl 2 rows of a 3 row repeat. The first row is knit, second and third are purled. Can anyone give me some advise on how this is done? I have several books on stranded knitting and Fair Isle but nothing is said about purling in the round. Any help would be appreciated

Purling in the round is the same as purling flat.

If you are alternating colors, however, you need to bring the yarn not in use to the back and have the color that is in use in the front. When you switch colors, you switch positions. This way the carried color is stranded inside the stocking.