Knitters, in time, learn to read their knitting. Except for the first few blind-faith rows of a lace pattern, you can pretty much tell what your knitting should look like, and see at a glance (although not necessarily as soon as you'd like) that something has gone wrong.
Knitters ALSO learn to read a skein of yarn. Sock knitters, that is, and skeins of variegated sock yarn. For instance, I took one look at this (ballband lost):
and knew it was going to knit up into blue, brown, and white stripes. Since I think most striped socks belong on Pippi Longstocking (or someone with equally spindly legs), I opted for a pattern that would break up the horizontal stripes in an interesting way. Grumperina's Jaywalkers: