accentText property
The accent as a text colour on the chat's backgrounds (quick replies, outlined buttons, links, prices): the site colour itself when it reads at WCAG AA (4.5:1) on the page, bubble and card backgrounds, otherwise the nearest darker (light theme) or lighter (dark theme) shade that does.
Implementation
Color get accentText => readableOn(accent, [palette.bg, palette.surface, theirs]);