Crocheting a blanket with squares without having to cut and join the yarn together is what I did in this current crochetafghanpattern. Using yarn colors of green and gold for a Green Bay Packers fan and a size M crochet hook.
For this pattern I used Caron Natura One Pound Yarn in Sunflower and Kelly Green. Beginning with a size M crochet hook my starting chain was about 150 to 160 single crochets. The remainder of the afghan was double crochet and I changed the yarn colors as I went along, crocheting over the existing yarn.
The basic pattern is yarning over the new color on the last stitch of the previous color to make the color change clean. Continue to switch colors back and forth every few stitches until the end of the row.