You should be able to get this effect using templates:

• make a new film
• add some subtitles
• set them to your preferred colour, effect etc.
• File -> Save as template...

Then when you make a new film, specify that template and all your subs should get the saved settings. How does that seem?

I see. Yes, that would work. However, I think this is a suboptimal solution. It makes sense to change the defaults if one wanted to use always the same settings. Templates are for cases when one needs to switch between a few different settings frequently. Not for setting defaults -it is still one step more to specify a template. But it is something I can live with.