isnms-
How many miles were on the plugs? How do you drive the thing (pedal to the floor, stop and go, mostly freeway, etc)? Do you consistently use the same gas? Any fuel additives? All of these things will effect the carbon build up on the plugs.
Taking a blind stab without knowing any more about your car, I see a few things:
1. cyls 1 & 2 run the coolest, closest to ideal a/f, and generally run the the cleanest. I would imagine you are running an un-equal length manifold (1&2 have longer exhaust pulses).
2. cyls 3&4 look ok - #3 looks to either have too much fuel (slightly lower comp) or burning a hair of oil. regardless, the combustion process is dirty enough to leave its mark. Nothing to really worry about, but something to watch.
3. #5 looks par for the course. Looks like a little pre-ignition, which would make sense if your timing was off. It doesn't looks out of the norm with the rest.
4. #6 - what kind of oil are you running? It looks lean, but no more than the others under high heat (no additional graining or discoloration compared with the others), but is definitely funky under lower heat. Granted, #6 runs a bit warmer anyway (the egr design doesn't help), but I have never seen that much difference without there being another problem at hand. I personally would start looking at that injector (assuming the comp test and leak down performed with reason to the other 5). If you were eating a little oil (say rings that were begining to exit stage left), I could see increased cyl pressure helping minimize that. But I would also expect the electrode to show a little more of that.
Don't know if that helps you out much or not. I spent more than a few years tuning engines with spark plugs (and an egt if I was lucky) - the only way to know more is inspect the crown and combustion chamber, but it helps if they are clean beforehand.