Worst case scenario if you'll have an active link light with no connections. If you bought the cable from the store, you're probably safe. If you made it yourself you'll want to use a cable tester to verify it is correct.
Emerald and Riser are right. Really what it comes down to are that the wires on each end are crossed correctly, not that it has to do with any specific color. Example, all of the wires could be different colors, or the same color, but as long as the wires are switched correctly on each end then you're good.