Raised pavement markers come in a variety of reflective colors, some of which (like white and yellow) have guessable meanings borrowed from painted road line conventions. But there are other colors to (like blues and greens) that relay more information to those in the know. Some colors cue police officers, emergency personnel or maintenance workers, showing them where they
In the USA I assume, given that the person assumes everyone is from there too?
Looks like a UK article
The article goes into detail about various different countries, including the USA, UK, Australia, etc
This is for sure a thing in the US as well.