I've had fun with my new HU last couple of days. JVC, thought I'd give it a go. Got the perma +12v wired up no worries, but for some reason it had an extra connection on the red after the ISO adapter. Looked dodgy to me, but ended up being the correct connection for the Ignition feed - yellow did sod all, finally gave up and plugged both into red.
My previous HU, a Sony, was a yellow/red swap after the ISO adapter tho.