The shell is a dark brown.. I don't know much about guns but anyone know anything?
"Winchester 30-06 SPRG" is a marking I'd expect to find on a .30-06 Springfield cartridge.
The .30-06 was adopted by the US Army in 1906, and has been a highly popular cartridge for both military and civilian uses ever since. Your cartridge could be over a hundred years old, or it could have been manufactured yesterday.