I also have a thing about lighting. Like I should be attending a twelve-step for it. ("Hi, my name is Aaron, I have an LED problem. Hi Aaron!")
As mentioned in the thread about the green truck, I use the FlySky FSi6, which along with servo channels, spits out everything on what they call iBus. This is basically a serial connection, just like you'd get on your computer, ideally suited to connect to an Arduino. It only requires two wires, data and ground, to transmit up to 14 channels.
Add battery power and all of my trucks and trailers can then use a standardized small plug for trailer lighting.
That's the Arduino in question, hiding in the trailer toolbox. Very little to it, and few if any external components. The LED strings do like a little filtering to their power, which is why the electrolytic capacitor on the right.
The LED's are actually RGB, ie can do any color, but are programmed to mimic a 1:1 trailer.
Front marker/turn signals are orange
And rears marker-turn-brake lights are red.
I did cheat, and the centers turn white in reverse even though you rarely if ever see a trailer with backup lights. I was having fun, and it's all done in software, so just requires reprogramming the Arduino to change behavior.
Turn signal looks like
https://youtu.be/AmvBJAILeNM
and backup lights
https://youtu.be/r39fU8mcJMI
and, if the RX can't get a signal from the TX, it blinks like hazards:
https://youtu.be/9Ie0TLF9iFk