Nellis is home to the 57th Adversary Tactics Group, whose main purpose is to simulate the aircraft and tactics of potential adversaries throughout the world. The 64th and 65th Aggressor Squadrons within the group fly F-15 Eagles and F-16 Fighting Falcons. The IMAX film, "Fighter Pilot: Operation Red Flag" provides an excellent look into just how closely the 57th mimics foreign threats, including their paint schemes.
I believe that that F-15 wears a Flanker style camoflauge scheme with a medium gray radome and two tone light blue gray camouflage. Just a bit over from this Eagle is one in a two tone desert scheme, also an aggressor.