I don't know what caused the discoloration on the Bates card, but it appears to me that the top color was removed throughout the background.
Starting at the bottom the yellow and blue were layered to produce the light green grass. The dark green run covered most of this area to produce the deep green grass. This top dark green layer has been reduced and in a few areas removed from the Bates card.
Where the ground meets the horizon the dark green run produced the purple. This top layer has been removed.
The top sky portion was produced with the blue print run. This area and has been removed.
I added a Ritchey which has similar color patterns simply for comparison.
