stereo wiring/ color change?! e36

[Spot]

Anyone know why/ where wires from stereo change color before they are routed to the speakers? My manual doesn't show an equalizer or switcher,....
If this is the work of an aftermarket tweek, they did a factory looking job!
I switched an Alpine to a Blaupunkt cd receiver & instantly lost signal to the speakers. I have verified that there is output at the unit and have run wires directly to the front speakers for temporary tunes, but am hoping someone will save me from having to tear out the driver's seat in order to follow where the wires go before changing color and running to the speakers.
Thanks!

[da_bull]

A lot of those cars have a factory amplifier, it may just not be turned on. Check and make sure the blue with a white stripe (not a solid blue one) off the Blaupunkt has power when the radio is turned on and that it is hooked up where the Alpine was hooked to.

[Spot]

Thanks for the quick response. The old & new stereos had identical wiring- I just carried over everything as it was, but I'll check for power at the blue w/white stripe wire. But if there's an amp, where else might it be besides the left side of the trunk? Anywhere else BM ever mounted them?

[da_bull]

Its usually on the left side of the trunk like you mentioned, but I guess someone could have relocated, but probably not.