black (slightly lighter than the background) here, on a dell tft.
This one is also set quite light as well, I did a picture of the morning sky a few days ago, on my monitor at home the buildings and road were very dark, almost silouette (same on hte monitor at work) on this one here I am on now, its was all lit up and easy to see.
So I am guessing on the other monitors I use, the coat woudl be close to invisible.