By which I mean, the Mediterranean coast has loads of colourful seaside towns The Amalfi coast (see Vernazza for an amazing example, or the other four Cinque Te

By which I mean, the Mediterranean coast has loads of colourful seaside towns The Amalfi coast (see Vernazza for an amazing example, or the other four Cinque Terre, or Pixar's Luca for a well-observed only slightly exaggerated version), Menton in France is very colourful, Venice has very colourful bits… Roman houses, much like their now-white statues, were very colourful, so I suspect they spread their love of coloured plaster wherever they settled. Though I am not an historian (IANAH).