Marly Bird has been doing a lot lately with planned pooling in crochet, but the same kind of thing works in knitting, too.
Crafty Crusader wrote a post a while back about using planned pooling in a hat project, which pointed me to the Planned Pooling website. This site allows you to plug in colors and note how many stitches are worked in each color as well as how many stitches are in a row and whether it’s worked flat or in the round.
This allows you to see what a knit up swatch or garment would look like, and you can play with the numbers to get different effects." ~ Sarah White, Craft Gossip site