you are supposed to go when you see the third yellow light light up. Once you get more practice you will have to wait a little longer but when you are new at it go when you see the third light. I will bet you will still have a .6 or so reaction time but it will get better and that is where alot of races are won.
2001 sangria zx3, best 1/4 time 15.70 @ 85mph. Now have an 04' Pontiac GTO w/LS1