Well, this pissed me off. Apparently I got a half and half mix of siding with a light colored backing and a dark colored backing. The light color is how I remember all of my house siding. I must have gotten half of a new run (its been a few years since the house was done now), all of the box part numbers were the same. Somehow, I got lucky and all of the upper stuff I did had the light backing and the lower rows of the long side were all lighter.
I figured out something was wrong when I did the two rows above the window. I cracked into a new box and I had one dark piece above a window and another a couple over. I was like wtf is going on here??? It was barely noticeable, but something was clearly wrong. So I took those rows off and made sure each even row came from the same box.
I didn't realize it until this afternoon when I was picking up the pieces I threw off in anger and was marking them to not use. Then I went and checked all my boxes and I have about half and half.
The good news: when used in the same row, you can't tell if you have a darker row above or below a lighter row, again, I only noticed this looking down the line of my siding in a shaded light.
The bad: This just sucks. Now I have to pay attention to what pieces I put up. Again, You can't tell as long as the rows are even, but if you overlap a dark and a light something looks clearly wrong.
I don't normally bring stuff back, but this is something I would... if it hadn't been almost 2 years since I bought it