I'm actually wondering specifically how many Lord/Lady Magisters each collage has now (Including the patriarchs/matriarchs). These are the ones recorded in Codex's Rolodex post which I didn't think to actually look up until I had nearly finished writing this post:
Average is roughly four.
The Grey's have eight, and I think we can assume that they are an outlier.
Lights have Mira, Alric, Egrimm, and Elrisse at minimum, so at least four.
Jades have Pan's mother, Pannaoth and Arburg at minimum, so at least three.
The Brights have Reicthard, Olenus and Thyrus Gormann for three again.
There were two potential Amber candidates at the duel, plus Dragomas and Luuk Schild who made the dragonstone, so that gives them at least four.
Golds have Gehenna, Stanisława, the nameless challenger who tried to kill Dragomas ,and Feldman, so again at least four.
The Celestials also had one challenger at the duel, so with Maria that also makes at least two.
For the Amethysts we only know about Elspeth I think?
So including Patriarchs/Matriarchs, that's 29 confirmed Lord Magisters, for an average of roughly 3.5 per college. That suggests that there's maybe for or five LM's we don't know about yet—probably in the Amethyst and Celestial colleges, who we've had few interactions with.
And yeah, there are a ton of Grey LM's, it's actually kinda scary just how many there are, but I suppose the Grey's have higher standards in who they recruit and train, which leads itself to being more top heavy.