This video teaches the secret to change the color at the end of a crochet row. An excellent summary is given below. First do the last double crochet by wrapping around, stick it through your last Stitch, wrap around again, pull through and stop. Grab the second color, leave a little bit of tail, put it on your hook and pull through all the loops. Grab your new color leaving the tail, wrap around and pull through for chain 1, again do the same for chain two and turn it around. To continue wrap around stick it through the first stitch, wrap around again and pull it through all three loops. Repeat the same process for the next few stitches. Follow the above steps and try to change color at the end of your crochet row all by yourself.