To do the colored lights, you need to time everything. You can't change the color on a light with a trigger as far as I know, but just like you have done, you can use 3 separate lights which are the colors you want. You can use one trigger point, but you'll need to time the delays for the triggered items and the light duration correctly on the lights themselves.
You can decide on the time and the order of the colors, but for this, I will assume 2 seconds for each light and go from Green to yellow to red. First set each light to a duration of 2 seconds. (You probably alredy know, but just in case: this is done on the light itself, not in the coaster trigger screen). Then when programing the triggers set Green to turn on with 0 delay, Yellow to turn on with 2 second delay, and the read to have a 4 second delay. This should sequence them to turn on AND off at the right times. Adjust the numbers appropriately if you wanted it to be 5 seconds each or something. Sometimes it's handy to change the names of each of your lights to say their color. So much easier to select the right one when adding the trigger items.
Unfortunately, the lights have that annoying feature that even when they are off, they look like they are turned on when looking at their face. ...they don't flood light out when off, but you do see them. To eliminate this, you can select them and use control X and then push them just behind the wall. The light generated by each will pass right through walls so it will still light your tunnel, but the annoying base color won't be seen at all
I hope this helps, some of these triggers get a little complicated, I have been working on a ride with lightning and trying to time the lights, the sparks, the explosion, and the speakers gets pretty tricky. At one point the thunder was happening before the lightning....LOL.....fail! Fixed now.