Not sure, I think I have seen something similar when the grass was mowed when it was wet. Fungus invades the cut surface. Not serious. Gone with the next mowing. Could be due to the cold also. Some types of dark green Kentucky bluegrass are very slow to green up in spring--I am not so sure about off color in the fall...but deep roots are not present yet. Also, you should always ask about the sod harvest and storage conditions--the second batch of sod was fine. The first truckload was potentially stored on the truck too long, as in overnight. Retained on pallets at the sod farm for more than 8 hours. Unloaded at the site, but not laid for 6 to 8 hours. Discuss this with the sod farm; they may not be willing to take the blame--but they have seen it all.