Tail light wiring color help

[naps45]

2006 A3 8P
I see four wires for the taillight wiring assembly: Brown, Black w white stripe, white, and grey. Can anyone please identify what functions these wires are? I know brown is ground but I can't find ANY explanation after lots of searching!! Lots of wiring diagrams, but they aren't helping.
I just want to put a resistor on so I can run LED brake lights. So I need to know which is the brake wire.
Please help!!

[Silicon Voodoo]

ask somebody to brake while you look at a voltmeter and see what happens. also put a Hall effect clamp to measure the current so you can calculate how much resistance you need to set. but i'm not sure how the computer determines that a bulb is burnt, if you set a LED, the current curve could be a non linear weirdo that will get you to constantly have warnings.

[naps45]

I really don't have much experience with things electrical...but I appreciate your response. I'm sure it is accurate, but I'll be doing more research. I have a multimeter now.
I know that I'm measuring DC with a setting of about 20. But I'm not sure how to test if a wire is the turn signal or brake , etc. It's kind of annoying the little amount of information out there for newbs like me. I do appreciate your response, it's just a bit overy head given my limited experience.

[Silicon Voodoo]

Did you check that thread https://www.audizine.com/forum/showt...ty-on-all-LEDs!
maybe their shop can drastically simplify your work here

[Silicon Voodoo]

I found out that there are bulbs that incorporate the correct resistor so they're plug in compatible. I ordered new turn signals yesterday on aliexpress.
https://auxito.com/pages/search-resu...s_Tail%20Light
I'll keep you up to date if it works