I feel like I'm missing something big in terms of customizing the colors. It must be a common question, but I don't see anyone asking about it in any of the usual places. I haven't been able to find any documentation on how that might work. I figured out by trial and error that the .css file is not overwritten if it is changed and the command is re-executed. I haven't figured out how to change the colors of the tables in the diagrams. Any pointers would be appreciated.
Well, I guess I figured it out. You need to generate a set of files, then tweak the image files and style sheet, then replace them in the .jar file. When it regenerates it uses the ones you've put back in the jar. So, every style change requires a jar update as far as I can tell.