These helicopters have the same paint scheme of the Marine One helos. I can't find any reference to this paint sheme on this type of helicopter though. I'm guessing they are Special Air Mission helos used for VIPs in the DC area but can't find any documentation of that anywhere.
Info Requested, Helicopters - Parked
By: kjfitz
They're based at Quantico, and often operate out of Anacostia, but that doesn't mean they can't use Andrews as a handy base to keep a few birds close to town.
http://en.wikipedia.org/wiki/HMX-1
https://www.hmx-1.usmc.mil/
I found reference to "Some Marine Corps UH-1Ns were converted to VH-1Ns as VIP transports, including six for Presidential use." I'm guessing that's what these are:
http://en.wikipedia.org/wiki/UH-1_Iroquois
http://en.wikipedia.org/wiki/1st_Helicopter_Squadron
http://www.afa.org/magazine/jan2001/0101heli.pdf