The aura (glow) you're seeing around the plug wires if voltage leakage thru the wires. This is just from working on other vehicles as I'm still learning on my 420. In my opinion you shouldn't see this with a brand new wireset but someone with more experience will have a better explanation. I wouldn't think the coil itself is suspect since you're seeing it at the wires themselves.

__________________
1983 300SD
1988 420SEL