The Swiss, being a little bit slow to make changes, probably copied the Austrian's love of yellow paint for road markings.

When I lived in Bavaria they assured me the Austrians chose yellow paint against the German's white choice, to help their Winter snow clearing workers.

These poor chaps were never achieving their work bonus as they wasted time trying to clean the white markings from the roads. Once the Austrian highways management changed to yellow paint they were all much happier, and the roads were cleared quickly.