I found the wiring color codes for the 1999 Magna at EUROVOX
http://www.eurovox.com.au/EurovoxWeb/Downloads/Wiring%20Diagram%20Update.pdf
I searched all over and even paid for a download which had the wrong codes before I went to the Eurovox site . Hope this helps someone wanting to change the Radio/cassette player.
Cheers
reg8892

that is a good find. but when i changed my stereo i just went to autobarn and bought a plug that plugs into the stock harness and has all the same wire colours as the one that came with my cd player, so i just wired that up in my spare time at work, took it home and plugged it all straight in.