Green does imply safety - that's why you see it at so many hospitals.
Personally, I don't care if they're wearing pink with yellow stripes, as long as they have signs up warning me that they might be in the road.
I happened around a curve on Route 28 in Wolfeboro yesterday and had to slam on the breaks because the traffic was at a stop due to road construction. I knew the visibility/stopping distance would be especially short for whoever came up next behind my van - sure enough, it was big honkin' 18 wheeler. He laid down a nice strip of rubba before stopping behind me. The Argelets thought it was "cool!" - I thought I was gonna be sick...
Yeah, that was a wide-eyed moment, if there ever was one.