I've attached a file to this forum post, quest501options.zip.
Extract the contents and copy to C:\Program Files\Axe Software\Quest
(or the same folder under "Program Files (x86)" if you're using 64-bit Windows)
This adds a Tools > Options window where you can override the game colours.
Please give it a go and let me know if you encounter any problems. It will be part of the v5.0.1 release if all goes well.