I tried a few combinations of (Dark/Light/Auto) On Mac with (Dark/Light/MacSettings) with Sourcetree, and there is a bug :
if you using Dark layout on Mac, and You switched from Light to Dark in Sourcetree, you can't go back. the solution is to switch the light mac theme and switch st to light again. and switch to the dark layout at mac again. but its a bug, i wish was fixed.