If you're ignition is fine, they'll all be a spotty tan texture/color. A darker gray and fuel smell is a sign of an ignition problem, leaving unburnt fuel residue on the plug. Since you have to pull them, and they're cheap, I generally replace them when I do this. Just remember which cylinder you found which plug in, if you find a problem.
My bad coil was getting worse at higher temps. It would be better at cold idle, getting progressively worse as the car warmed up. My bad alt contributed to the condition, by means of a weak spark. A new alt, battery, and 3 new coils solved my prob, but I'm glad I didn't just shotgun it. That can get expensive.