Disk in Sky with Bright Turqoise Colored Ring Light

It was a clear night sky, no clouds in sight, and as we were getting off the highway in a fairly rural part of Maryland, we saw an oval shaped object outlined by a bright turquoise colored ring light that was flying over us. This object was clearly the shape of a disk, as outlined by the blue light it was emitting, and you could see its disk form because the sky was clear enough to do so. It also flew across much faster than a plane, and it was too rural for anyone to operate a drone, so it wasn't a drone either.