I was wondering if anyone had a good formula or pics for repainting the blue/grey imperial models to the more grey/white color that is one some

yes I want to know this too.

currently I'm planning on using Administratum or Ulthuan grey with a light nuln wash

Administratum grey works really well and almost matches. I did a striker and a F/O fighter which almost matched the tie advanced paint color. You might just want to add a little bit of white to it.

https://community.fantasyflightgames.com/topic/257270-fort-defenders-repaints/?page=4

**knock knock**

This is the Imperial Security Bureau. Open up. We've been made aware you are soliciting Top Secret Imperial technology. . .

Vallejo Field Blue.

I second Ulthuan Grey with a dark wash. I used that method on my TIE Elite Defender:

I also use Mechanicus Standard Grey if I want something darker:

That is spot on, love the Mechanicus giving it a slightly more evil look.

Just thinking out loud, would using a Drakenhof Nightshade wash give a Administratum coat the bluish tint for that other version?