While we still call them “the boys in blue”, it has occured to me that I haven’t seen a [US] police officer actually wear the color blue in over 10 years. The pattern I’ve noticed all across the states is that city cops wear black and county cops [deputies, I believe they’re called] wear tan.
What’s the dope on this?
In Chicago, the police officers wear black pants and light blue shirts.
Fayetteville, AR: Navy shirts and pants.
Madison, WI: Light Blue shirts, Dark Blue pants.
Navy pants and shirts in New York. Maybe you’ve been watching too much “Reno 911!” 
Just this weekend I found myself having a polite conversation with an officer from Foristell, MO. He was wearing a light blue uniform shirt and navy blue pants.
Many city cops wear dark navy (blue) uniforms, which look a lot like black. See this page for official LAPD uniforms, which look black, but are referred to as dark navy in the description.
'Bout 15 years ago when I was an undergrad, members of the school’s NROTC unit wore their uniforms to classes one day a week. Which uniform varied, but it was often what they casually referred to as “blues.”
Even standing right next to one, in perfectly good lighting conditions, these “blue” uniforms looked black to me.
Now, I realize that the line between “midnight blue” and “black” may be pretty fine; was my color vision failing me, or were this uniforms really made from black fabric and only called “blues” out of tradition? Whichever the answer, might it help explain the perceived “blue-less police” described in the OP?
I’ve heard that more and more police departments are moving toward more tactically-aware uniform colors. It seems that lighter colored shirts attract more bullets.
Australian cops wear blue.
My uniform is a dark navy blue, which is officially called “LAPD Blue”.
I think every other city cop in my county wears some shade of blue uniform. Black is becoming quite common in other areas, though.
In the Washington, D.C., area, I belive I’ve seen just about every color combination – all blue, all black, all grey, light blue shirt with dark blue pants, white shirt with black pants, grey shirt with black pants, various combinations of tan and brown. I don’t think there really is a standard and I doubt there ever was one.
In summer the shirts are the light blue though.
Phoenix, Arizona police wear black “blue,”…even in the summer 
Short answer: The uniforms are black. They are referred to as “blues” out of tradition.
Longer answer: There are two distinct uniforms that you may be referring to. The first is “Service Dress Blues,” consisting of trousers, double breasted coat, and a tie with a white dress shirt. The second is “Winter Blues,” consisting of trousers, blue shirt, and a tie.
IIRC, the SDB coat, Winter Blues blouse, and trousers are referred to as “blue.” The belt, tie, and shoes are referred to as “black.” All of these items are in reality the same color (black), but it made for great inspection material for new midshipmen. (e.g. “What color is your coat?” “Sir, my coat is black, sir!” “Wrong! Your Service Dress Blue coat is Navy Blue! What color are your shoes?” “Sir, my shoes are…navy blue, sir!” “Wrong! Are you blind? Anyone can see your shoes are black!” ) Of course, the real goal was to get these officer candidates used to answering questions under pressure.
See the U.S. Navy Uniform Regulations for more info.
–robby (former NROTC student and Naval officer)
P.S. There is one more wrinkle, if you consider the U.S. Coast Guard. All of their uniforms have the same names as the Navy equivalents, but their coats, trousers, etc. really are blue.
Thanks, robby. The ones I remember most strongly sound like the Winter Blues.
Philadelphia: light blue shirts, black pants w/ light blue piping.