Thanks for the hint,
Version 47 is certainly a bit far from being realesed (we're at 44) and much can still happen.
If I check the add-on compatibility notes there seems nothing remarkably:
https://developer.mozilla.org/en-US/Firefox/Releases/47I`ll try to keep an eye to it and hope to have time to look into it when 47 reaches beta status.
(Not promising, because I'm quite busy a.t.m. But who isn't....)
B.t.w.: The color rules are a function (User CSS) that Firefox uses "nearly" automatic. But it shows that the add-on initializes at least correctly at Firefox startup.
Michael