On a UK motorway, the colour of the reflective studs depends on where they are:

  • Between the lanes on a motorway: white studs.
  • Left-hand edge of the carriageway / between hard shoulder and first lane: red studs.
  • Right-hand edge by the central reservation (middle barrier): amber studs.
  • Between the motorway and its slip road or at lay-bys: green studs.
  • Temporary lane layouts (e.g. roadworks): fluorescent green/yellow studs.

So if you’re specifically revising the classic UK theory-test question “what colour are the reflective studs between the lanes on a motorway?”, the answer is white.