N. nigricollis is a moderately sized, venomous snake with a moderately distinct head; the shape of the head is due primarily to two large venom glands found on each side of the head. Its colour can vary depending on region of origin. Some specimens are black or pale grey with a yellow or reddish ventral side with a broad, black neck band, often with an orange or pinkish bar on the neck. Other specimens can be yellowish-brown or have a yellow copper colour and are missing the bandings around the neck and the reddish colour on the belly. Some other specimens are deep reddish-brown, and yet others can be an olive brown.[7] Some can even be striped black and white.[8] There are 21-23 dorsal scales at the mid-body, 182-196 ventral scales, and 54-66 subcaudal scales.[9] This species generally grows to a length of 1.2 metres (3.9 ft) to 2.2 metres (7.2 ft). These sizes are subject to trends based on geographic location and subspecies.
