Sony CD player into laser

[KW XRT]

Frigged the old stereo by disconnecting the battery and not getting the code right for it {see seperate post** so bought the mrs a sony to go in the laser but found today that none of the speakers are marked - or + so first does it matter when wiring speakers to have them wired - to - and + to + or can you reverse them with to much of a drama. I reversed them in the past with old 5hit but with a brand new sony wanted to ask first.For instance the drivers door speaker is yellow with blue stripe and white with purple stripe.Also is there any way to tell the - wire with a meter or something.

$%%%$^%^ jap $%%^$$%%it