In Stargate, the Jaffa have a tattoo for the shape of the Goa'uld they serve. Some Jaffa have Gold ones that appear to be some kind of implant, while others just have a black one. It seems in general that the warriors have the gold version, while the lesser personal only have a black one, but I can't quite figure out what the exact pattern is. Anyone have an authoritative source?
It has to do with rank.
All Jaffa have a mark on their foreheads signifying the Goa'uld they are in service to. For most Jaffa, the mark is simple black ink. However, higher ranked Jaffa can be given more ornate, ostentatious tattoos. Jaffa in high standing have been known to be marked by a silver tattoo (for example Fro'tak), and the First Prime to a Goa'uld are given the gold embossed mark of their respective god.
So gold is the higher ranked, but some have silver as well to show high standing.
The leader of a Goa'uld's Jaffas have the title of First Prime. That First Prime is the Jaffa with the gold emblem. All other Jaffa under that Goa'uld have the black tattoos. When a Jaffa is made the First Prime, the symbol for their Goa'uld is carved into their forehead, then molten gold is poured into the wounds, which grants the gold coloring.
Teal'c described the process early in SG-1. You can read more on First Primes at the Stargate Wiki.