Sporadic misses in engine

I’ve eliminated the miss in my engine, I hope!
A few days ago while rounding a corner, tried to accelerate and the engine died. Took a while to get it started, and when I got it running the ‘transmission failure’ light was on. Limped home. Erased warning light with scanner. Took it for a ride, and had major roughness/misfires.
Marked all the coils and removed them. removed the plugs keeping them with their respective coils. Compared plugs and noticed that 2 plugs (2 and 5) had white tips that I thought indicated leanness in the gas mixture. The rest were shiny black. Reasoning that the car wouldn’t run at all with 4 plugs foul, that the two white ones must be the misfires.
Replaced first one coil then the second and the engine seems smooth to me.
Can anyone explain why a plug/coil that is misfiring would appear to have a lean mixture?
BTW I had the exhaust system repaired. I miss the growl of my cat, but it’s better to be quiet on long trips.