https://mutcd.fhwa.dot.gov/services/publications/fhwaop02084/index.htm

The use of red on signs is limited to stop, yield, and prohibition signs.
A white background indicates a regulatory sign;
yellow conveys a general warning message;
green shows permitted traffic movements or directional guidance;
fluorescent yellow/green indicates pedestrian crossings and school zones;
orange is used for warning and guidance in roadway work zones;
coral is used for incident management signs;
blue indicates road user services, tourist information, and evacuation routes;
and brown is for guidance to sites of public recreation or cultural interest.

Why bother remembering when you can just look it up in the MUTCD?

Ohhh so that's why "info" type components (toasts, modals, divs, whatever) are styled in blue for every CSS bootstrapping kit.