There's no single standard unfortunately, but many modern systems with four speakers do seem to share certain traits.
If you can find the bunch of eight wires going to the speakers you'll often find that they use one color for the front and another for the rear. The grounded sides are often plain wires, and the "live" sides get a stripe: one color for right, another for left.
An example might be:
Front left: Gray/Blue, Gray
Front right: Gray/Red, Gray
Rear left: Green/Blue, Green
Rear right: Green/Red, Green
Substitute other colors for any of those at the manufacturer's whim and you get the idea. I've seen it done the other way as well, where they use the base color to indicate left/right and the stripe indicates front/rear, although that doesn't seem to be so common.
If you can identify the eight speaker wires from the bunch, you can check which ones go to which speaker with an ohmmeter, so long as the environment isn't too noisy. Set your meter on a low ohms range and as you apply it to each pair you'll hear a slight rustling noise from the appropriate speaker. The stripes should then let you get the phasing correct, unless someone has fiddled with the connections at the speakers themselves.
