Actually Roman brown or a darker brown would be better suite dà forza fascist Italy and green for a liberal Italy (if such a thing can be said to exist) while orange would Word better for partiranno republics IMHO. On the other end, green would be... Ehr... About right... For a "Padanian" thing, especially if we Insubrians do get independent from those Padanian morons.
We already have 9 1/2 (the half is for the regular use of reserve colour) colours for Italy. I don't see the need to add one just for Fascist Italy, especially when we could just recycle one of these coulours whom ALL are unused for the period.
The best choice, IMO, is to do the same thing we did with China or France, aka using a unused colour : hence why I tought either using Lombard/Savoy colour for Italy (which would have the merit to fit the general colouring on most maps) and keeping Roman for Mussolitaly, either colouring it with IDK, Lombard coulour.
But really, at this point, adding new European colours should remain dictated by absolute necesity if we want to keep a readable key.
As for Padania, well, there's Northern Italy colours, with Ostrogoths/Milan colour for instance.
Lombards became a generic name in th Middle-Age, a bit like Cahorsins (from the city of Cahors). Most of Lombards weren't Italians, and arguing a cultural conclusion from this would be like arguing anyone serving French pastries comes right from Paris.This last, roughly corresponds to medieval Lombardy (from 900 CE on) is the least culturally Italian of them all, having closer ties to Austria and even Britain and Ireland (you'll find some Lombard Streets in a few English and Welsh towns, including IIRC London itself
I wouldn't answer all of it, giving it's not the topic, but all respect due, I think your point is formal and anachronic on several matters. For instance, there's no real linguistical sense having Gironda (which is not a river, but an estuary) coming from Gerundo.
At best, it shares a common origin "girus rundae", turning waters, which are evolving from Vulgar Latin on their own (altough there's room to understanding Gironda as a cognate of Garumna or other pre-IE names)