I'm using insulated #4awg stranded copper cdr for grounding a 120v/240v multifamily dwelling. The grounding cdr will be protected on the exterior of the bldg and then ran through the joist on the interior of the bldg without protection. The THHN insulation is blk in color, I have alway's wrapped green tape at 2'-3' intervals the entire length on the cdr to identify it as grnd. It has alway's been accepted (and will be accepted for this job ). I've read Art. #250 regarding identification of the grding cdr and I can't find where or why this is accepted. This is typical of many installations in Michigan. Does anyone know why this is accepted?