Firstly simple: use an array to indicate time and on/off status of led. Let's pick a number and its lowest 3 bits represent the 3 leds (RGY <->0bxyz), with '1' means on and '0' means off.
So your sequence is this:
0, 0b010, 0b100, 0b100, 0b100, //at time 0, lane 1's green is on, and lane 2..4's red is on
30, 0b001, 0b001, 0b100, 0b100, //at time 30, lane 1..2's yellow is on and lane 3..4's red is on
32, 0b100, 0b010, 0b100, 0b100, //at time 32, lane1's red is on, lane2's green is on, and lane3..4's red is on.
...
All you need to do in your code is to detect if the time has come to change the leds and then change them.