Gold-tinted canopies have been noticed on the EA-6B and the F-16C/D.  On
the EA-6B, the coating is a shield against electromagnetic radiation from
the Prowler's powerful jamming pods.  On the F-16C/D, officially the
purpose of this treatment is classified, but discussion on the newsgroup
has brought general agreement (based on unclassified sources and hints
dropped by pilots) that the gold coating reduces the aircraft's radar
signature, by reducing reflections off the complex interior shape of the
cockpit.  In both cases the coating is a very thin layer of actual gold
metal, not a gold-tinted paint.

Other aircraft, such as the F-15E and F/A-18C/D, have a distinct greenish
tinge to their canopies.  This is a different coating (on the inside of the
canopy rather than the outside) that reduces internal reflections to help
visibility.  Several newsgroup readers report having similar coatings on
their glasses, so it's not exactly a secret.