indiglo gauge question
 

I'm in the process of installing indiglo gauges. I was going to tap the + wire to the oem dimmer so the gauges go on when the the headlights turn on. There are 3 wires....ground(black), a red wire, and a red wire with a black stripe. Which wire do i tap for the positive??? The red or the red with black stripe??? I think its the plain red wire, but just want to make sure.

Is there any other ways to wire the gauges???

use a mulittester, try with each wire, one is probbaly constant, and the other will turn on with the lights, what kind of car is it?