Bulb with green covering for the turn signal indicator of the dash cluster. Mandated for Cougars sold in Minnesota in 1967 only,...we don't know either. :-)*NOTE*
Need help diagnosing a Cougar turn signal problem? Victor Yarberry is the world’s most knowledgeable expert on the subject. Vic has owned Cougars since the 1970's and is the designer of all of our solid state sequential systems. There is no question he cannot answer! Here is a link
to a great source of information on the subject.