Here’s how I change yarn colors so as not to interrupt the clean line between two different colored rows or stitches. In this example, I’m making stripes so the last row is completely red and the new row will be completely white. (In my photos, I’m showing single crochet stitches.)
Begin making the last stitch before the color change, but don’t complete it. (In this case, the last stitch before the color change is the last stitch of the last red row.)
Just before you yarn over for the last time to pull through the last loops on your hook; drop the current yarn that you’re drawing from and pick up the new color yarn and yarn over with the new yarn.
Pull the new color through the old color loops.
Here is the next color change…before