What does "in blue" mean? [closed]

You were, after all, brothers in blue

From TV Series Elementary S03E08, what does in blue mean here?


Without having seen the episode I can't answer definitively. Typically "in blue", or "blue" refers to Police, as in "thin blue line". Thus "brothers in blue" would mean members of the police force, which is often regarded as an informal fraternity. The association with "blue" is due to the perception that police traditionally wear blue, though many departments wear grey, black, brown, khaki or green. Comparable to the term "Green Machine" when referring to the USMC.