With wxSYS_COLOUR_APPWORKSPACE or wxSYS_COLOUR_WINDOW ?
I prefer wxSYS_COLOUR_WINDOW (only tested on linux).
Another weird thing:
I can change the colour to any non-default vaue and it gets saved on close, but if I try to revert back to default it is not saved.
Changing the caret's colour only has an effect if I close and reopen C::B or the editor, or if I open the editorsettings dialog an close it.
The caret colour setting is still possible via "Settings -> Editor -> Margins and caret", so it can be changed in two different places what can confuse the user.
If resetting the default is done by just not setting it, the old value must explicitely be deleted in the conf-file or it will remain.