old wiring colours

My friend has pulled out an old aiwa sterio from his car but didn't label the wires. i connected 1 blue(with fuse) 1 white to  12+ve , 1 thick black connected -ve, this gets the display ect working.but no sound, there are 2 red,2 black all showning +3v, 2 light blue, 2 orange showing 0v i assumed they would be the speaker wires but i carn't get any sound out. any suggestions would be great (he still wants to use the old radio)

Cheers

You said you got the display to come on, that's a start.  Have you tried hooking speakers to the red and black wires?  If not, you can always crack the case open and have a look (reverse engineer).  Find the output transistors which go to your speaker leads.