Why is an oxygen cylinder in the hospital always white

The paint of oxygen cylinders supplied by Hospital Medical Gas Cylinder Suppliers is white and black mostly to let persons know it's an oxygen cylinder, i.e obliging in the identification of gas, and also it makes it calmer for the anesthetist. There are many breaths of air present in the hospital fluctuating from usual oxygen to anesthetic gases like isoflurane, desflurane, etc.
So if any other gas cylinder is linked as an alternative to oxygen to a patient in a dangerous condition it may be lethal.