I'm very against green as a "warning color." Universally (in every country that I can think of), green means "go." While it might be brighter in some wavelengths, so many drivers out there are legitimately stupid and will just associate green with "go" (not the intended message of "slow/yield") if they seen green lighting in low vis conditions. I grew up in NY, and I honestly don't think that anybody (other than the people with the actual lights on their vehicles) knew what think when they saw VAS POVs with green beacons coming down the road.
Not only is Amber a bright color, but it is recognized universally as a yield or caution color (and even an emergency color in some countries), so I really think that they should stick to that.