I reckon One must be hard to beat. They have:

317/1 - bluey-purple (and are there still any LTS-liveried ones?)
317/6 - Cream/Red/Brown/Blue and One new livery
317/7 - Stansted Express (with most, but not all, units having the
composite coach painted up for a financial services company); One new
livery
315 - fGE; Intalink; Crimestoppers/BTP; family railcard; dirty grey
undercoat
321 - fGE
Anglia loco-hauled: Anglia; inter-city; Virgin
360 - Different fGE livery to other units!
170 - Anglia; One
150 - Anglia

And I bet I've missed some.