Yes your correct, on this lens there is a green dot, that is for automatic aperture setting on the ring. But it was interesting to find out, that when this "N" switch is set to the right, as the arrow directs, a physical stop is put in place. One has to first push the metal tab counterclockwise, then activate "N".
(**This image shows the lens disassembled, having trouble putting it back together again,
Sigh:
(there was a url link here which no longer exists)