Some of the things that can cause parsley to yellow is too little water or too much water. If it is too wet the roots can’t get any air. The plant needs certain nutrients to grow but too much can also be a problem, especially too much nitrogen. It can burn the roots. I’m not sure how much fertilizer you are using or what kind but I’ve turned plants yellow and stunted or killed them with too much nitrogen.
It’s not that unusual for parsley that has just been transplanted to turn yellow, especially if it got a little dry before it was transplanted or if you did not water it well at transplant. If that is the case, it should come back fine since you said parts were green. If the parts at the growing tips are green, I would not worry about some yellow down low.
If you can take a shot of the whole plant, that might help.