markdownAlertColors

Alert accents in the hues GitHub draws them in, one set for a light surface and one for a dark.

Blue for a note, green for a tip, purple for important, amber for a warning, red for caution -- the association a reader already has from the page an agent may well have taken the alert from. The values are close to GitHub's default themes rather than copied from them; what matters is the hue, and a caller who wants an exact palette passes their own.