I have Mac Sierra 10.13.6 I’m using Scrivener 3. When I’m in Compose Mode, and I highlight text, the text turns grey, and when I highlight text, the highlight is only grey. If I go out into the regular editor, the colors do show.
This is intentional behaviour, because colours that would work with black text are unlikely to work well with white or light text. So, if Compose Mode uses an override colour for its text, highlights and text colours are also overridden.
All the best,
It works in Scrivener 2 and Scrivener for Windows and even Scrivener 3 for Windows BETA. There is no reason why it shouldn’t work in Scrivener 3 for Mac. It must be a bug.
You can adjust the text selection highlight colour in the Appearance: Composition Mode: Colors preference pane, with “Text Selection”. While you are there, you might want to adjust how things look from the defaults, if you prefer to see colour. Click on “Text” and disable Override text color with color, and then adjust the “Editor” setting so it isn’t so dark and you can see black text again.
In older versions of Scrivener, if you used the text color override setting like this, text on stuff like yellow highlights would be impossible to read. Now you can read them, that’s the main that has changed in fact. Most of the rest works like it did in v2 with the override setting. Annotation colour would be suppressed as well, Preserve Formatting highlights would change (that is now extended to custom Style highlights too), and hyperlinks would use a different colour.