Rated 5 out of 5 stars
... as said it is sadly not compatible with the latest FF Version (14).
There is also another way to run it atm:
Just download Nightly Tester Tools 3.3 and after installing it go to:
Extras/Nightly Tester Tools/enable Force Addon Compatibility.
You can then activate RedShift again.
So far i didn't notice any problems and the theme works as usual.