It looks like either a sticker or some kind of slip on label. You can actually see a small part of the real toothpaste's logo under it.
It can probably be reproduced with some glossy sticker paper and a cleaned up image of the logo. I doubt it would hold up to actual use if you went that route, though, and condensation may cause it to peel if you leave it in your bathroom.
Actually it was "feldergarb" in the writer's guide, according to Battlestarwiki! :lol
I remember them saying both "feldergarb" and "felGerCarb"... but it was just another silly madeup word that they weren't consistent with. It's like keeping track of how long they think a "centon" is (minutes? weeks? :lol)
Hate to say this but it has always been "felgercarb" as per Dirk Benedict aka the original Starbuck! It was his favorite word along with "frak!"
This prop will never be 100% screen accurate until someone can come up with the actual flavor and if it infused with anti-cavity/gingivitis fighting properties!!!!:lol