Closer look 1. This shows pretty well that there is sky where hay bails should probably be taking up space.
This shows a closer look at the blue spot and the un-erased areas of red. A much closer look can be seen here.
Much larger image here showing red hay.
Flag in the hay bands.
larger view here
The sky is there because there was no hay bale in that position. That position is behind the flag when looking straight at the stage, hence no need for hay bales back there. I don’t know what the red color in the hay is, but it isn’t from the flag. Why would there be red spots in the hay bales behind Obama’s chair? That isn’t anywhere near the flag.