Coming from maintenance as my previous AFSC, we typically do not prefer blues of any kind. (But we were always in them for the things you have listed above + getting in trouble as a flight/sq).

PME graduations should be marked as an important event to the graduates, and imho, should be service dress. You worked hard for your achievements, and you should be proud of them. Your family members that attend these graduations (in person or virtually) see this as an important accomplishment.

Promotions and retirements I think should be up to the member. In order to create this pride to wear your history of how you got to where you are, that should be enforced by associating positive memories of your blues and not just with the negative memories.