Green, for "all good, lets go!"

At least it should be, since e-stops are usually red for "crap, stop!"

There certainly are double-meanings here, depending on one's perspective and what one defines as "good" and what is "evil". Depends on if you're the operator or the mechanic, I suppose.

I see below that your machine seems to be the opposite. Most machinery I've seen has a green "start" button and a red "stop" button. I guess they're not as standardized as traffic lights. The hard part is when you press the green button, which illuminates the red warning light, lol.