Oh dear, you really have no clue at all.
It actually makes so much more sense to have both default to red, from both a safety and convenience point of view.
If both default to green, two cars approach in opposite directions at the same time, one (or both?) of the lights change to red, but the driver goes through as it is changing. I'll let you figure the rest out.
If you always default to green in one direction, then when someone arrives in the other direction and reaches the red light, then the lights have to assume (for safety) that another driver may have just gone through the green. They then have to leave enough time for that 'imaginary' car to have driven through, before they can change the red to green in the other direction.
Whereas, if both default to red, then the lights just have to make a decision as to who arrived first and can immediately change for that driver. This is not only the safest way to do it, but also the quickest for the driver as well. Which is why most temporary lights work in this fashion.
While your always green idea may seem sensible to you, it is by far the worst thing to do.