I own a 2004 Chevy Classic Base Model. I am trying to wire a red led light strip to the brake lights so that when I hit the brakes it will illuminate. I am planning on mounting it in the center underneath the rear bumper so it illuminates the ground. My problem is what do I tap into. In the tail light housings there is a plug that has 2 light possibly baby blue wires, a black, a brown and a green. I was hoping one of those run the 2 brake light bulbs. That would be easier than running the wires to the body control module. But if I did have to, I don't know what color wires run the brake lights. If you could help that would be great.

 

Greetings Red welcome to the Forum.

Sounds like you don't have a Trailer Connector, and are trying to tap into the wires in your Taillights...I think I read that correctly ?

It's really hard to ID those wires by color, they vary at times, so...
You should get/or build a Lamp Probe with a sharp pointed end, it sorta looks like an Ice Pick, with a Ground wire.

Just get your turn signals blinking, probe into/through the insulation of the wire back there, and when your tester starts blinking...you got that side. Then do the same thing on the other side.

Once you've located the wires for the Turn Signals, they are the same wires which light your Brake Lights. Just do a Saddle Connector onto the Wire, and add the appropriate (side) of the Strip to it for each side. Those things usually have Plastic Housings, so you'll have to run a Ground Wire to a convenient location as well.

Here's a link to what a Tester looks like...
Dorman/Conduct-Tite electrical multi tester (86598) | Circuit Tester | AutoZone.com_

Good Luck.

PS: One other possibility...
Somewhere around your Spare Tire back there, there may be a stub of wires sticking out of the Wire Loom, where a formal Trailer Connecter would be attached. You might/should be able to probe and access the L & R Turn Signal/Brake Wires at that location too.