I used 3 colors of Hobby Lobby I Love This Yarn! in turquoise, gray mist and ocean and a size I (5.5 mm) crochet hook. I had 2 skeins of each color and had leftovers of all three. Finished size of my afghan that is 8 strips wide is 50" long x 49" wide. I worked the 5 round strips, joined them together, and finished by working a border around the entire blanket.
You can make the blanket larger by adding more strips or adding more stitches in multiples of 3 to the first round of the strip.
I used 1,520 yards of yarn in 3 colors: Colors #1 & #3 - 456 yards each and Color #2 - 608 yards.
You could use just 2 colors and alternate them every other round or use a main color and use scraps for the other rounds.
The five page patterns has complete written instructions and two crochet charts -- one for the body of the strips and another for the border. This pattern is a free download available through my Ravelry store.