I don't remember where is which part, but yes, that's the part of Cicada's profile with Dio's name. I always wondered about Guild uniforms and couldn't make sense of who wore which color either. No wonder, Dio was trolling Guild uniform traditions, so there was no way of figuring it out before Chronicle. But the Dio weirdness aside, it's anything he/she wants for the Maestro, black for the chief agent (forgot the position name) and whoever's next in line to be Maestro, gray for the upper rank agents (Scutum), white for the lower rank agents (Aspis). Both Scutum and Aspis meaning shield. After that, each job has its own uniform, all mostly white. I don't remember what other Principals wear.

Gotta love Dio trolling uniforms and his entire team following along.