WOOOOOOOW!Hundreds of thanks!
I've managed to do what I wanted after launching that PowerShell script!!
BTW, I also set this in _variables.scss:
$font-size-base: 1rem !default;
This gave me an even better and more harmonious look of all UI elements compared to setting 'font-size:1rem;' for body directly in bootstrap-forum.min.css.
Well of course you can directly modify the css, its your decision. But its much easier to modify the scss files.
Changing just $warning color from $purple to $orange gives 37 (!!) differences between the new and original bootstrap-forum.css. And you should know why - we have derived RGB values and the like. So changing resulting CSS's for bootstrap themes directly is definitely not a way to go 😊