Much like brioche bread is soft and buttery, brioche knitting produces a very airy and spongy fabric that is ideal for soft pieces like scarves and cowls. Knit in one color, the basic brioche stitch produces a reversible fabric. But two color brioche is where things get interesting. Some of Marchant's examples of variegated yarns used in tandem are absolutely gorgeous.
Marchant offers a Craftsy class, "Explorations in Brioche Knitting" that offers visual instruction as well as two scarf patterns. I made the Alex scarf with two colors of Spud and Chloe Sweater, a soft worsted blend of washable wool and cotton that I purchased during the Steel Valley Yarn Crawl.
It's important to pick colors that are different enough in tone that there is a good contrast between the lights and the darks. As an example, this is the same scarf in black and white:
You can see that the blue is light enough to really pop from the grey background. If I had used a darker blue, the effect would be muddied.
The only downside to brioche knitting is that it does use a lot of yarn. I used every bit of both skeins, and I would have liked my scarf to be a little longer. Also, when knitting two color brioche, you knit each row twice, once with each color. It goes quickly, though, and I didn't find that to be a problem.
Here's a link to my Ravelry project page if you'd like to see more about the pattern and the yarns I used.