At first I thought you were referring to the color of his outfit, to which I thought, "Isn't Li Long's costume orange?" And then I realized you weren't talking about his clothing...I would PMSL if yellow is the placeholder for Li Long, nothing controversial about that. XD
Okay but seriously, I have no clue who YELLOW could be. A guest? A re-designed Yun-seong with a yellow color scheme? I have no clue.