Not to worry! Changes in the pH of the skin is what causes the green. When we sweat it shifts the colour of the bronzer making the red inactive, leaving you with blue and yellow = green. Some skins don’t even need to sweat to have this reaction.
This can also be caused by using a tan eraser too close to getting a spray tan. These products are very high in pH!
When you shower, only about 80% of the bronzers wash off which is why you still look green after your shower.
By your second or third shower, all the bronzer will have washed off and the green will go away.
It is impossible for you actual skin to turn green from the tan, it is just the cosmetic bronzer that needs to be rinsed off properly.