In most cases, the surgeon wears a white apron, but during a surgery he is wearing a blue apron, why blue?
Initially surgeons did wear white in the operating theater, but there were two large problems with this. Firstly, under the bright lights, the white reflects too much light making an inordinate amount of glare making it difficult to see. Secondly, the white cloth highlighted the red blood which many people found objectionable. As a result, most operating theaters have switched to either a blue or green colored cloth. This reduces the glare and when the red blood gets on it, the cloth appears black.
Some hospitals do identify specialties/departments by different colored scrubs, but this is outside of the operating theater. Inside the theater, most specialties/departments within the same hospital wear the same color.