Teal can go with many almost all brigades and I prove with just about every deck I make.
I'm purely speaking out of ignorance here, since I don't splash teal into many decks, but how does it have much synergy with white? What about gold? For that matter, I don't think there's much synergy with purple either. Again, this might just be my ignorance, but without using a spread offense (read:Sam), I don't see how splashing teal into anything but green is going to be worth it. Yes, white has Teal/Tomb, but I've yet to see anyone use it this season, and even if I did see people using it, it's just not as good as it was a few years ago.
The colors they don't go well with are Silver and Blue and the Sam theme is so fast and enough power that Teal would be a waste of card space.
This is just incorrect. I actually recently took out all of the teal in my deck but Aaron, but I used teal for a very long time, to great success.
In conclusion Teal is the best support brigade hands down closely followed by silver. Teal is powerful but in a very different way. Silver is not as powerful because it can't mono and its support isn't quite as good. I hold to my word, make any deck except for the ones above with 5 or 6 teals cards it will be much better.
It's certainly not hands down the best. I think a lot of people would agree that silver is actually the best support brigade, between Angel Under the Oak, Angel with the Secret Name, Cherubim, and Captain of the Host. I also outright disagree that adding "5 or 6 teal cards" will make any deck much better.