Sure, it’s done.
https://github.com/discourse/discourse-trendy-login/commit/50e16393021786b564c47a839ffcdcd6b6fb2f6d
It’s not trivial to follow the site theme entirely in this component but what I’ve done now is that the component will follow the theme’s primary and secondary color. So the background and text color of the box will look similar to the site’s theme and the contrast will be better.