Is the marked wire + or -

[install4you]

Hi. This is the only electrical forum I'm on so I apologize if I'm totally off base with this subject. I also apologize if y'all don't like DIY'rs. I was in a trade for 28 years (not electrical) & I'm usually more comfortable talking with pros.
I'm installing a backup camera in my car and, as is common, the red/black power line to the camera is too short. I'm extending it with an all black line with a white stripe on 1 conductor. AI on Google seems to think the white stripe should be negative & the unmarked is positive but, depending on how I word the question, I've gotten opposite answers. I want to follow standard practice whenever possible.
My logic, without the actual knowledge, says the marked conductor (stripe, ribs, printing) says "with" current (+ or hot) & no marking says "without" current (- or neutral).

I know this may be making too much out of too little, but details matter. My #1 motto before I retired was "the only way to be right most of the time is to aim for perfect every time."

So any help is welcome. I'm sure everyone will all agree with your answers.

BTW, my #2 motto was "Often late but worth the wait!"

Thanks, Eddie

 

[Alan]

Wire markings aren’t standardized for polarity. Some manufacturers use stripe for negative, others don’t. Always verify with a meter before connecting and mark it yourself once you confirm.

 

[install4you]

Thx. Got it done successfully. I knew to get the polarity right by testing. I just wanted to follow standard if I could. I don't even remember which way I went.