Currently, dashboard etc. trigger severity background colours are configured via the frontend and result in inline CSS. Inline CSS overrides themes and any CSS file customizations. Default colours are too "loud", optimizing for a light background theme makes things even worse for dark themes and vice versa...

I've previously asked for the ability to include a small customization CSS after the theme itself is loaded; Would be better, if one customization CSS URL could be specified per theme.

(I'm probably going to hack the frontend pages, stripping out the inlining and moving the definitions to the themes, but that makes updating a bit more painful - again...)