Alpine HU Remote on wire

[AlpineM30]

car 1989 325i (Standard sound) I have a alpine head unit and was wanting to hook up a amp for some subs. I was wondering which wire is for the remote? I thought the all blue wire was it but that is already occupied I found a free blue wire with white stripe, could that be it? I have also been researching and some people said on the alpine harnesses the red wire is the ignition wire. The car was recently professionally wired by Cartoys. Any help would be great.

[yanal]

after market Alpine head unit ? if yes how is the blue wire occupied ? if it is a trigger wire you can splice the amp remote wire to it, it only uses few millie amps so your good.

[Van Westervelt]

I think the blue wire if for antennae, and the blue with the stripe is for signal aka amps.