What is the symbolic color of Saint Luke?

St. Luke is the patron saint of:
artists
bachelors
bookbinders
brewers
butchers
doctors
glass makers
glassworkers
gold workers
goldsmiths
lacemakers
lace workers
notaries
painters
physicians
sculptors
stained glass workers
surgeons
unmarried men
Worshipful Company of Painters
Capena, Italy
Hermersdorf, Germany