The default GUI is really a low contrast and washed out version compared to the old one.
I noticed, that there are chances in the settings to change colors, but not all. 2013 Windows style looked like this.
Check the latest MS Office Outlook ribbon - no longer low contrast - crisp and clean symbols and high contrast. I don’t think people who write, want to see grey text on light grey backgrounds.
Please, make the default a high contrast and then some people, who may have sensitive eyes, can change the theme to more bland. This is supposed to be a functional tool - and I don’t feel it is if you have hard time reading the text!
Most, if not all, of the fonts in Scrivener can be changed via Options → Appearance ->Fonts.
Background colors for many areas of Scrivener can be changed via Options → Appearance ->General.
A few of us are working on creating stylesheets that change the default colors, because inside Scrivener, changing some of the colors is not possible.
This is relevant to my interests, since a lot of buttons and things aren’t as visible as I’d like (like index card lines…) I just chalked it up to a WINE issue.
Index card lines can be changed in Options → Appearance → General (tab) → Colors → Index Cards → Index card lines. You can only change the color, but you can make them pretty dark.