Just finished an inspection on a newer (2004) home and noticed that some of the ground wires in the service panel were a different color. (Purple) There did not appear to be any signs of overheating. Has anyone came across this before.
Not me but I wonder did you scratch one to see what colour it is inside
I also see two white wires under one screw not proper.
I like to see the Grounds twisted especially when some are different sizes going into the buss.
Where there any double taps on the breakers if so not proper .
I wonder was the purple caused by some chemical in the area like Cat pee , Bleach or sulfur water in the home
There are 3 grounds under those terminals. No good!
Says who?
Are the grounds the only area where you saw the discoloring? Could Chinese drywall be a possibility?
That’s a blanket statement that will get your butt in hot water around here!
2004, discolored copper, as Skyler stated Chinese drywall a distinct possibility.
The panelboard neutral bus is typically listed for one, two or three EGC’s but only one neutral conductor.
Going by the posted pic it does not look unusual to me I see it often. Did it look like the plumbing pics attached? The darker ones are the cold pipes. Wires pic from last inspection, 2011 house. Pretty sure that condensation causes it. Panel boxes mounted on concrete is going to be cold, and there may be cold air leaking in through the conduit. Cold in MN and AB. Why some and not others? No clue 
