I had a migraine trying to answer that question.
The priest in the center looks like he is the main celebrant because he is in the center...but he is just wearing a stole over his alb.
The other priests are either wearing just an alb or a chasu-alb.
The deacon on the left is positioned properly while the one on the right looked like he got booted by the other concelebrating priest.
So who do you think is the main celebrant?
If it it were really the one on the center, well, he is not dressed properly for the occasion.
Same bull you get here from priests who don't dress properly, giving you the same bull that what is important is what is in the inside.
Dear Fathers, read the parable of the wedding feast. A poor guy gets booted out just because he was not wearing the right dress.
GULP EXAM 2: Guess the name of the priest in the center