This is not the best order but I ended up going Yellow, Kole, Powder Blue, Regal. All months in between adding. Everyone is fine and get along.
The Yellow picked at the Powder Blue very bad for 2 days and then settled down. I also taped pictures of other PB to the glass the day I introduced. That seem to help.
Powder Blue did not bother the Regal at all.
All fish are about equal in size. Tank size is a 150.