From what I remember, this was a plug-n-play install. I shortened some of the wires, hence the soldering station.
Also, for as long as I can remember, GM has used the same colored wires for the taillight harness. I believe it may me an industry standard.
The brake lights are a little different=
It depends on if the car shares brake and turn signal bulbs, which the Cruze does not. I believe the brake light wire should be blue, but I am not sure.
On the systems that share bulb duties, the brake light signal coming out of the brake switch is white. It goes up to the turn signal switch. The turn signal switch directs the brake signal into the turn signal wiring, green and yellow wires. The third brake light on these systems is a blue wire out of the brake light switch, that is why I believe blue should go to the brake lights. But I haven't confirmed that on my Cruze.
Looking at my manual, the colors change depending on where on the wiring harness you are.
Something you need to keep in mind: the Cruze is a highly computerized car and is wired differently then older cars. The left stop light and right stop light are separate circuits. Likewise the left and right tail lights are separate circuits. And EVERYTHING is driven from the Body Control computer, not some switch that could easily handle a few extra amps. I'm not sure how happy the BCM will be with the added load of the trailer.
I'd suggest looking for an adapter that's specific to the Cruze. Presumably they've figured out the best way to do things - or at least a way that's known to work.