to follow-up on my own theming challenge above, I’ve adapted all themes with the new color cycle based on -40 being primary color in themes · GitHub
could be helpful for others, and please comment if you find something odd 
way more in style than the default colors
bottom line
default uses
--color-primary-05: #001721;
--color-primary-10: #002e3e;
--color-primary-20: #004156;
--color-primary-30: #006787;
--color-primary-40: #009ac7;
--color-primary-50: #18bcf2;
--color-primary-60: #37c8fd;
--color-primary-70: #7bd4fb;
--color-primary-80: #b9e6fc;
--color-primary-90: #dff3fc;
--color-primary-95: #eff9fe;
so I used each primary color of my themes as color-primary-40 and set the others to be an increasing series of colors
Late Edit
this worked up to b4.
As of b5 and release those buttons no longer get the theme variables, but default to the system defaults again. No idea what was changed yet
issue: color palettes in themes not loaded · Issue #26415 · home-assistant/frontend · GitHub