Luke AFB is not just home to a load of USAF F-35s.  It is also the training base for many of the export operators.  They also allocate some of their jets to the unit, so you do have the opportunity to catch a bunch of jets that are not from the USAF.  This includes Italian, Danish, Norwegian and Dutch jets.  Aside from the Danish ones that actually have a tiny bit of color in their national markings, all the jets are low viz.  At least they are slightly different, even if not very conspicuous.