For drag racing the green light goes on 0.4 seconds after the last orange light, so you need to react in 0.4 seconds to leave at the green light (in practice you need to react much earlier to account for the time it takes the car to leave). That time doesn't actually reflect their actual reaction time though, humans have a much faster reaction time than that.

Mildly related F1 fact: the green light at the start line comes on a random amount of time after the final red light comes on. This interval can be between 1 and 9 seconds.

Interestingly, the actual release signal to start an F1 race is the red lights going out, not the green lights coming on.

The green lights release the cars to the pre-race formation lap.

There haven't been green lights at the start for many years now. The start signal is the red lights going out.

But you're right about the randomization (although I don't think 9 seconds is right, I've never seen it take nearly as long as that)

This is sort of normal for any FIA standing start. Green light comes on at a pre start chosen, fixed interval between 0.2 to 3 seconds after last red light goes.

F1 has its own dedicated specific rules not seen in any other circuit racing.

Rolling start involves green light coming on at about 50m from the start / finish line and if stays red, start is aborted.

On a pro tree, the three amber lights all come on together with a 0.4 second delay to green. On a sportsman tree, they come on in sequence 0.5 seconds apart and the green is 0.5 seconds from the last amber light on a sportsman tree.