This snake largely retains these colours for most of the first year and only when it gets to close to 1 m does it change into subadult colours and with the eyes changing colour to a brownish green colour. Compared with many other snakes, the head is large and stubby and the eyes very big. At this stage the strong keels on the body scales are visible. Subadults are largely soft shades of brown or green as can be seen in photographs 4 – 6. As they grow and after a few more sheds they assume the adult colours.

Females are largely brown and males green, but not always. Individuals from the Western Cape often have a dark brown or even blackish band down the back with lighter brown sides (photograph 7) or in Gauteng or elsewhere a more plain dark brown overall colour (photograph 8).

Adult males vary tremendously in colour with most males from KwaZulu-Natal, Mpumalanga, Mozambique, Eswatini, Gauteng, Limpopo, Northwest Province, the Northern Cape and elsewhere further north being bright green in colour (photograph 9) or bright green with black between the scales (photograph 10). In the Western and Eastern Cape males are usually blackish above with yellow, green or even orange sides (photographs 11 and 12). Adult Boomslang have dark eyes.

Although it is generally said that this is one of the snakes where we can distinguish between males and females by looking at the colour of the snake, it is mostly so but not always. We do see green females and brown males from time to time.

People are easily confused with green snakes and the most abundant green snakes are the green bush and water snakes of the genus Philothamnus – particularly common in coastal KwaZulu-Natal. They are long and thin and very alert but can be confused with young Green Mambas. Young Boomslang (under 1 m in length) are never bright green in colour and have keeled body scales which the harmless green snakes and Green Mamba do not have.