Greenish stain

I was a house Friday and it had a green stain part way up the furring strips. It appears as though it is used to look like or to make non-pressure treated lumber, to look like pressure treated lumber. I wish I had pictures, but I don’t. Anyone know why this is used and what it is?

It could be a mold resistant application that is becoming more popular in the lumber industry, with all of the problems it looks like they are addressing some of the problem on their end, however the green stain should appear on most of the board.

everyone is going green these days.