This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Which color is given to the “progress of treatment" cephalometric tracing, according to American Board of Orthodontics? 
Select and explain. 
A. Black, B. Blue, C. Red, D. Green
B: Blue
Answer: B: Blue 
Explanation: In order to facilitate identification of consecutive cephalogram, the following colour code for tracing has been suggested by American Board of Orthodontics.