Green’s Dictionary of Slang

tan-tracker n.

also din-track rider, tan-track rider
[tan track n.]

(orig. Aus.) a homosexual man.

B. Hudson First Aus. Dict. Vulgarities n.p.: tan tracker, an aggressive homosexual.
Aldrich & Wotherspoon Gay Perspectives 44: Ride the tan track and tan-track rider and din-track rider are only marginally less blunt. The same idea is involved in the variants on chocolate.