Well, the Grand Order alliance book shows that some of the Freeguilds base their colors from ancient tribes that took their icons from the-world-that-was: the crowned skull of penumbra= Reikland, Sanguine lady of flames= Talabheim, Stonehearted Blood Bull= Ostland, etc.
Besides that there's the Freeguild from Azyrheim who most likely use blue, gold and white like the Devoted of Sigmar do.
The Freeguild regiments from the foundling cities and newly raised provinces and fortresses made in the reconquest of the realms have yet to be shown.
There could be mentions made in the novels that I'm unaware of so I'll raise the question on Dakkadakka to see if any auxiliaries were detailed.