I recently learned a super simple way to change yarn colors for crochet projects! Like this one for example--
How To: Chevron Crochet
When you get to a point in your crochet work where you need to add a new color, you will start a single crochet. You should have the 2 loops on your crochet hook.
Instead of yarning over, and pulling through, you're going to add the second color in.
To do this, make a loop with your second color. (Leave a short tail.) Put your crochet hook through the loop of your second color, and pull through to complete the single crochet on your first color. Perform one chain stitch to finish it up!
Then, tighten your yarn by pulling the ends to adjust. Once your work is nice and tight, trim your first color. Be sure to leave a tail the same length as your second color's tail, or your work will fall apart!
Pull both of the tails behind your work, and single crochet over both of the tails.
Do this for 6 to 8 single crochets, and then trim what's left of the tails.
Hope you found this helpful!