we are currently renting out a building with in-ceiling speakers. There are 4 speaker wires (blue, orange, white with a blue stripe, & white with an orange stripe). We would like to hook these wires up to a computer to play Pandora through them.
Is this just 2 speakers? A speaker will have a positive and a negative wire, I'd assume the blue's g together and the orange go together, which is positive and which is negative I couldn't tell you without looking at the reverse of the speaker, but generally I think the striped ones are negative. I took a quick look just now and have looked before but I do not recall ever seeing a sound card that takes raw speaker wire in as an output, I think you will need a receiver in between.
Since those are ceiling speakers there is a very good chance that they are constant voltage units(either 70V or 100V) in which case you will need a constant voltage amplifier as a normal amp will not work.