MG CAR OWNERS FORUM

Just like my 2017 G30 M-Sport, I'm currently having a rear diffuser installed, complete with an F1-style brake. From the diffuser, the wiring is straightforward. It looks like a power and neutral cable, with a red and black colour scheme. However, I can't seem to figure out where on the wiring loom for the back tail light these two wires should go.

My understanding is that the red wire from the diffuser attaches to the brown wire on the back of the tail light. Having the following cables on my tail light has left me bewildered regarding the black cable.

Blue and brown
Colours: Grey, Green, and Yellow
To gain authority, brown

Does anyone have any ideas how I can get this done?

Finding the brake light wire is easiest with a multimeter.
I thought red turned brown, right?
Since broken is often associated with earth, I'd say that black represents that.

My multi-meter is missing.

This is what chatgpt had to say about the brown to red. Now I'm really perplexed.

With their versatility and low price tag, multi-meters are a must-have tool.

Even if that were true, I'd be completely confused about how to use it. It would be more convenient and economical if someone here could assist me in determining when I need cables.