I was stationed in Fallon, Nevada after the Navy had moved Top Gun there. The F-5's are flown by VFC-13 "Fighting Saints." The Navy Strike and Air Warfare Center "NSAWC" (which encompases Top Gun) flies F/A-18A's and B's, F-14A's and SH-60's. As far as I know, Top Gun (or any Warsaw Pact States for that matter) never opperated any black F-5's as seen in "Top Gun." Check out the sites listed below. Good luck!
Here is a website with pictures of the different VFC-13 markings:
http://m2reviews.cnsi.net/scotts/features/krausevfc13a.htm
Here's someone's F-5 modeled in VFC-13 markings:
http://ansmodelisme.topcities.com/SECOND/plane/f5final.html
Here's another site with some reference photos:
http://clubhyper.com/reference/f5dp_1.htm
Internet Hobbies sells a decal set for VFC-13 markings here:
http://www.internethobbies.com/internethobbies/twobob172f5e.html