Best way for small tweaks of theme in PSU

Hi, I’m looking at making minor changes to the theme, like adjusting major colors to a corporate style guide. I can see how I can replace the theme entirely, but it’s not obvious what the best way to make small tweaks would be.

Is there a way to get the current theme as an object in order to modify it? Or do I have to replace it completely with something I make from scratch? What would be the preferred way, changing the CSS or creating a PS object to the -Theme parameter?

Best regards,

Product: PowerShell Universal
Version: 2.x