A-frame A-frame sign advertising balloons black and white blue books booksale color colors colour colours green orange promotion red sale sign alert car care concern prevent prevention protect protection risk risk area risky safeguard security theft risk vehicle warning warning sign white area cigarettes danger direction environment health health risk no smoking no smoking in this area sign not allowed pollution prohibition unhealthy advice appropriate behavior appropriate behaviour black dangerous directions emergencies emergency safety signs yellow advisory avenue calle cityscape crossroad crossroads highway intersection lane object pedestrian pedestrian crossing pedestrian sign road roads roadway street street scene streets caution communication go interstate light stop traffic traffic light traffic sign visual visual communication yield