Which one is OK? Or, what do you say?
(by car etc.)
The signal was green as I was passing.
The signal was green while as I was passing.
The signal was green when I was passing.

Question

Answer

1 is good. Also "as I passed".
2 is no good and beyond repair.
3 is no good, but could be rephrased "The signal was green when I passed."

In all cases it would do no harm to add 'it' as the object of 'pass', "as I passed it" etc.

Answer

The most natural way to say it I think would be 'the signal was green when I went past/ went through it'.