I am sorry.... but I am going to be the thorn amongst the roses here..... to me, the jacket looks black.  (sorry)

When i read *grey* , i think medium to light grey.
You possibly would have been safer to describe it as dark grey.

As we all know, the colour perspectives on our computor screens can vary from one screen to another, so it could have been possible that your buyer thought that the colour image seen on their screen was darker than they thought your description of *grey* may have been, then when receiving the item it turns out to be dark grey (or IMO, light black) then obviously, to the buyer it is not the colour they thought they were getting.

I should add..... black comes in many shades as does grey, white, green, blue etc etc..... one man's grey is another mans black.
ANNNNNNNNNNNNNNNNNNNNNNNNNDDDDDDDDDDDDDDDDDDDDD  I would also like to add that my eyesight is slightly diminished atm, due to cataracts which may/or may not affect my visual perspective of colours at the moment.... so whose to say that something similiar isnt happening with your buyer?

But to me........ your jacket is black. (light black, but black)  [I'm sorry]

And while I'm at it, since I'm already in the dog-house, what's with the statement... *I generally post within 4 days of cleared payments.*

I certainly hope two of those days are Saturday and Sunday!
Otherwise, Id be stating something along the lines of *I can only post items on a Thursday* 
I wouldnt be happy if my seller had my cleared payment for 4 days befor posting my item.  (just my opinion of course)