Shouldn't it be obvious by the placement of the light (red at the top)? I know some lights are foolishly installed sideways, but most are vertical.
Yes, the position does matter, but I don't think in colors and arrow has always meant GO. I have had to learn that there are now red arrows in some places. There are some places where there is only a single flashing yellow or red light (yellow=caution - red=stop then go when safe -- unless there is also a sign I stop to make sure.
Two lights are better than one...
Yes, two lights are better than one, but they are not often labeled witch light is what color and why. Most people don't understand that about 30% of the males are color blind to some degree and most of those are red/green.
Aaron Z