On my test device the screen to configure the “Messages” notification category looks like this:
The “Blink light” option needs to be enabled before K-9 Mail will allow you to change the notification light color (until then the setting is grayed out).
Some device vendors seem to ship modified Android versions that won’t allow you to enable the notification light. Some don’t even allow you to configure a custom notification sound.
I have no such settings menu in the “system settings”. If I want to enable the notification LED and choose the color, I have to conifg that in the specific app, e.g. WhatsApp or Threema (both instant messengers).
However system-wise I have one switch under notifications where I can en/disable the notification LED in general.
I just tested the Beta on my S7 and it seems to be the same: option to select LED color is disabled - but color is set (maybe still from pre 5.8xx version).
So far I cannot enable LEDs 
. Will try further to find such setting
I also only find a global LED enable/disable setting which is enabled and for other apps I can perfectly set notifications, e.g. Signal or Threema.
Should it work now with latest beta? I tried but do not seem to get LED notifications although I have now enabled and set specific LED color for an account in that beta:
Did you update to K-9 Mail 5.911 and then changed the notification light color under Settings → [Account] → Notifications → Notification light?
@stphn It works for me now. Although I would have missed the change without the notification of your new message.
I didn’t have to change any settings in the android settings. However the notification LED option was disabled in K9 settings. By choosing a color there the LED works again now.
Yes, updated and enabled the LED notification. (Was set to disabled before).
And it seems that now also the vibration is no longer working for me.
Will try a bit longer but for now it seems to be worse than before for me.
Ok, it does not seem to work for me with 5.911: neither LED (I have enabled it, was disabled before) nor vibration ( worked before, set to default).
@cketti : I guess I need to send a log file for further help to you? Is there a different way to export log than to use adb for it? If I remembler correctly there was a PR for that? Is that integrated in Beta version? If I need to use adb then it might take some time as I have no working computer at the moment…
Under Settings → General settings → Debugging select Export logs from the menu.
@stphn
Just to be sure. You set the ‘Vibration’ option to Default/Pattern and regarding the LED you specified a color there?
@AnoOoobist : yes, see screenshot
@cketti : I have enabled the extra debug logging and exported it an hour ago. Where to send it?
@stphn: Do you maybe have quiet time enabled? That will create “silent” notifications, which means no sound, no vibration, no notification light.
No, quite time is disabled
I have created a ticket and attached log there. Please let me know if you require more information.
@cketti thanks for having a look at this. Your latest comments on github ticket pushed me into right direction - it was the same issue and solution as for my other thread
For whatever reason my notification settings whent back to importance medium/no sound - but it should have been importance high/quiet.
As it was working with 5.80x before I joined Beta 5.911 it might be an side effect of this update. But maybe it was some manual changes as at the same time I tried to make LED notification work with that Beta.
Apps can’t change notification categories once they have been created. So K-9 Mail is creating a new notification category based on the old category (and deletes the old one). However, some things can’t be set by the app, only by the user. I believe an importance of high is something only a user can change. You’ll have to redo this change in the system UI every time you change the notification settings (sound, light, vibration) in K-9 Mail.
I just checked by changing LED color. Importance level stayed the same (high), but the sound setting changed from “quiet” to “unknown sound”. Have set it back to “quiet”
