New dyes from Unidentified Dyes ?
The specialty dyes like the Enameled and Molten dyes? No, those can only be obtained from the limited time dye packs sold on the gem store. They can be traded however so check the trading post for players that are selling them.
Besides the specialty ones, have they ever added in some new hues ?
No, you can see all the sets here:
http://wiki.guildwars2.com/wiki/Dye#By_Set
Hrmm, interesting – a new set incoming?
Ok, thank you very much.