Change Facebook Messenger notification sounds?

No way to currently change tones for any notifications on the Watch. I would love to see this feature as well and I am sure it will eventually come to the Watch. It is a very new device, be patient.

http://apple.com/feedback

Feel free to give feedbakc

Sorry. You cannot set custom ringtones for any third-party apps

How about starting simple, can we change the ding to be different between the messages and mail app?