How can I change that back?
Can’t find it in the preference settings
Which app and OS versions are you using?
And what exactly do you mean by the preview bar (colour)? The preview area at the bottom of Edit view, when it is switched to inverted?
“The preview area at the bottom of Edit view, when it is switched to inverted?” <— That one, yes.
I’m running macOS 10.12.6 and the latest Glyphs beta (1176).
No fancy Dark Mode stuff.
True, 1176 uses the predefined Licorice color, which is 0% saturation and 8% brightness, or RGB #151515. Version 1172 still had #000000 or 0% brightness. I can file a bug report if you like.
That is a side effect to for preparation for macOS Mojaves Dark Mode. I’ll have a look.