I think Knitting Guy is doing his Irish Hiking Scarf in a varigated yarn, and it looks incredible. It definitely adds a different look to cables, which can be a really cool effect if you're going for it. You should just pick out some variegated yarn you love, a cable pattern you love, and give it a try :D
ETA: And now that I've seen where suzeeq's link leads to, I realize that ONCE AGAIN, suzeeq says exactly what I was going to say RIGHT before I was about to say it.
lol