I've been reading on the net that red colored plugs are signs of cheap fuel or fuel additives. I pulled out three of my plugs today and while there are no signs of buildup or obvious lean or rich conditions, the ceramics have RED (< slightly brighter than this) tan rings on the ceramic insulators. This is the first time I've seen a plug this color, however. I've seen pink ceramics but this looks like blood.

I run either Shell 93 unleaded or E85- is it the E85 or do I have a potential problem?

 

I saw the same thing on my old plugs!