For a newb, probably not easy. For a pro*, fairly straightforward with access to the item or (less sstraightforward) decent photos and dimensions. That said, it will vary a lot depending on the badge.
Would a respray not be an easier way to effect a colour change?
Newb question: How easy is it to 3d a copy of a existing physical object? I have a simple car headbadge I'd like in another colour.