Let's cross on the green light.
You should cross at the red light.
I've heard both expressions used, but not sure which one is right.
I've also seen on the internet that
You cross at, on, with a green light, and the meanings are slightly different
But I don't know the difference of those.
What is the right preposition?
I think the most idiomatic expressions are:
Stop at the red light
Proceed when the light turns green, or when the light is green
The next most preferable would be:
a car proceeds on a green light
you may cross with/on a green light
There is something a bit odd about "cross at the green light". However,
If you are standing at a green light, there's no reason not to walk across the street
