I've found that cuffs often look "fluffier" from the purl side. Now, you could cut the main color, tie on the contrast color, knit one round and then purl, purl, purl. But there is another way.
Hold the stocking and join on the contrast color so that the inside of the stocking is the RS and the outside is the WS. Purl the first row only -- the knit side of this row will be on the public side of the stocking and will make for a smooth transition. Now, knit around so that you are forming reverse stockinette stitch on the public side of the work. Keep knitting until the cuff is double the length you would like it to be. On the sample, I knit about 65 rows. Don't bind off yet.
I've made the cuff extra fluffy and strong by folding it in half and stitching it down. In the first photo (upper left), you see the nice row of red and white bumps. This is the view from the inside of the stocking. You can see the rounds and rounds of knit stitches in white. In the second photo (at right) I've folded the cuff so that the knit side of the work will be hidden inside and the fluffy purl stitches face out for the world to see. Make sure you line up the wales (vertical columns of stitches). You're going to join both ends of the cuff and bind off at the same time. Put a dp needle through the 1st white bump, then through the first st on the left-hand needle. (In my photograph, the live sts are on a metal circular needle, the dpn is the wooden needle.) It looks like the second photo. Knit through both stitches as if you are doing a three-needle bind off. Repeat.
The second knit st has been pulled through both the st and the white bump, but the old st has not yet been dropped off the circular needle. There are two sts now on the dpn.
In the middle photo, the left needle has been inserted for the bind off.
In the last photo, the first st has been pulled over the second st in order to bind off.
From this point, just keep repeating these steps around -- knitting the st and the bump together, and binding off. At the end of the round, break the yarn and work in the end as invisibly as possible. You can even hide the end inside the doubled fabric. Below and behold, the final result:
This beautifully bound-off edge is on the inside. The cuff itself is double-thickness and reversible, and could even be folded down for a rakish, boot-like appearance.