Yes, Paul. I created a custom palette. I also modified existing classes in the custom code section of the template. I created new classes to work with both light and dark backgrounds of different colors and put them in the custom code section. I applied the new, custom classes in the settings of the elements.
What I found was that the custom classes were being applied even on section and elements where I did not want them. I also discovered that removing the custom classes from the custom code section did not remove the code from the custom.css file for the template.
Part of the problem, I'm sure, is that the code didn't cascade as I had anticipated. What I was trying to do was to minimize the amount of css that I would have to specifically declare for each section and element. It just didn't work out for me even if I tried to make the changes by overriding the default preset color schemes.
I also found that when I turned on the advanced features for scss and other code optimizations, some of the custom classes that were not behaving correctly suddenly started working.
Pagebuilder is an amazing tool, and it's very complex. Maybe I ran into something that doesn't work as I anticipated; maybe it doesn't work as the designers anticipated; maybe I was doing something incorrectly. Regardless, I did a lot of redundant styling, but it works.