while the texture is perfect, it seems that some of the color is off between the original wall texture and the dirtied one
just take some of the green tint off the dirtied one and it should be good as gold

image example: (copy and paste url)
http://ganonscrub.com/images/secret/hidden/source/folder1/folder2/folder3/homework/(porn)/door number 3/portal 2 collab stuff/tint.jpg