Yellowish Brown Residue around Coilpacks

[Spinal]

Need some help,
finally got around to looking at the engine as there was some yellowish residue.

Residue (it's not as yellow as the image would suggest):

Coil pack (there was evidence of water in the coil pack rubber)

Also some evidence of water around the spark plug when removed:

My first (worrying) guess was a leaking gasket to the coolant, but there's no mayo in the oil or the coolant that I can see.

Could it be just stagnant water? Any ideas?

I've cleaned the residue off, will try driving around a bit next weekend to see if it re-develops... but in interim, if someone can offer ideas I would very much appreciate it!

M.

 

[Spinal]

Trying to get the images back:

Residue (it's not as yellow as the image would suggest):
http://www.ndanka.com/wp-content/uploads/2015/05/Screen-Shot-2015-05-04-at-18.58.30.png

Coil pack (there was evidence of water in the coil pack rubber)
http://www.ndanka.com/wp-content/uploads/2015/05/Screen-Shot-2015-05-04-at-18.58.38.png

Also some evidence of water around the spark plug when removed:
http://www.ndanka.com/wp-content/uploads/2015/05/Screen-Shot-2015-05-04-at-18.58.09.png

 

[alfantasti]

Previous owner or car dealer may have got a bit enthusiastic with the pressure washer, forcing water past the rubber seal on top.
Once water is inside, where the spark plug sits, it would be difficult for it to evaporate back out.
The discoloured stuff is just the rust that has built up inside.

 

[Spinal]

Thanks - that worries me a lot less! I was starting to have images of a cracked head and coolant leaking all over the place...