This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anesthesia Machine, Subject name: Anaesthesia
Colour coding of halothane , isoflurane, sevoflurane and desflurane is respectively 
Select and explain. 
A. red, purple, blue , yellow, B. red , purple, yellow , blue, C. red , yellow, purple, blue, D. red, blue , purple, yellow
B: red , purple, yellow , blue
Answer: B: red , purple, yellow , blue 
Explanation: None