Every time I start Toad it starts in Dark Mode. I go in and pick a classic toad theme but it never remembers on next start. This is true whether it crashes ( which still happens too much ) or I manually shut down. Why isn't the theme preference retained?
What version of Toad for SQL Server are you using?
I can't reproduce the description of your issue in 8.1, FYI.
Even in earlier versions, however, Toad should be remembering your GUI display mode.
Are you changing it at the right place within the Options Base? Per snap below...
Toad for SQL Server 8.1.0.28168 (64 bit) For reference this screenshot taken after closing the app with ToadBlue 2014 applied ( call me nostalgic )
IF you haven't made too many changes to the Options Base and settings, try hitting the Restore Defaults link (upper right hand corner of your screen shot) to see if a reset of the options helps.
If not, I'd create a Quest Support ticket when you can.