Dark Mode Font Colour Settings

Hello smart MPU peeps. Can anyone explain a little about how Apple is choosing alternative default colours when iOS or Mac is running Dark Mode? Some of those secondary colours for DM are pretty wild. We have just been working with clients to polish their email brand identity and it all looks great until it goes thru the Dark Mode muncher. Only affects people using DM presumably but interested to know how much of this is controllable from sender end.

I’m pretty sure email.app uses the same html/css engine as Safari, you could use the prefers-color-scheme media query to provide you’re own?