jay32267 most likely already answered this - the headphones-level audio output have been green for 20 years or more. This is assuming your speakers have a single 3.5mm audio jack like normal pc or walkman/portable cd player headphones have had for 30 years or more.
Gets a little more complicated when hooking up a home audio receiver or digital audio or optical audio or a 4.1, 5.1 or 7.1 pc surround system to your computer but hey, I'd assume you'd have included those make and model names if that's what you were doing.