I think this is a bug, although it may be intended behaviour.
I now always use Logos in dark mode.
I got a nifty highlighting palette from another user which I used for the first time today (New Year's Resolutions and all that).
The lines/images in this palette are all grey. I wanted them to be more prominent in dark mode so changed the colour to white.
However, the highlights now appeared black.
I suspected this was due to dark mode, so I tried changing the colour to black and *voila* the highlight now appears white.
Is this intended? Or it is a bug?
For me, it seems counterintuitive. But perhaps this is the way L10 navigates highlights in dark mode.