Should I use on/at? Please help.

[scott833]

1) Every time I get to the traffic light, it was always at/on yellow.
2) The traffic light was never at/on green everytime when I was there.
3) Stop the car on/at red light.

[5jj]

1. 'at', 'on' or no preposition. We don't use 'yellow' for the middle light in BrE; it's 'amber' or, for some people, 'orange'.
2. The traffic light was never at/on (or no preposition) green everyspacetime (when) I was there.
3. Stop (the car) on/at red light/at/on the red light

'Traffic light' is fine; we also commonly use 'traffic lights'.

[English Freak]

I don't know what to say.
Suffice to . (this is correct in informal English.)