Kilgrave wears a purple suit in the restaurant where he is holding hostages. This is a reference to his code name in the comics "Purple Man".
The reference to Hammond Labs could refer to Jim Hammond, the original Human Torch from the early history of Marvel Comics.
Det. Clemons addresses Sgt. Simpson as "officer" rather than "Sergeant" after being informed of his rank. An NYPD officer wouldn't make that mistake. Furthermore, contrary to the common portrayal in TV and movies where detectives bark orders at uniformed officers, a detective doesn't outrank a police officer. In reality, all Sergeants (including uniformed Sergeants) out-rank detectives (although not necessarily a Detective Sergeant). Detective is merely an investigative track within the NYPD and doesn't confer the lofty status or deference that most civilians believe it does based on common portrayals.