QColorPrefs is a free, open-source command-line tool to create QSpice color themes and easily switch between them. Primarily intended to quickly switch between dark and light Waveform trace settings, it also supports schematic color themes.
If installed using the MSI installer, you can switch between theme files (*.qcolorpref) with a double-click in File Explorer.
This is a first public release so please let me know what you think and, of course, any issues or suggestions for improvements.
The QColorPrefs tool is currently available on the dev branch of my GitHub repository.
–robert