For example, the figures in the foreground appear as if they were stuck onto the canvas after the background had been painted. They weren't, of course, but the white accents, particularly on the shepherd's face, makes it appear as if they were.
The subdued color choices blend and unify everything to the point where figures become almost indistinguishable from their surroundings (note the flock of sheep behind the two figures).
The peasant woman's black and white striped skirt - which is a strange choice of pattern for a peasant woman to be wearing - is the only notable point of contrast in this canvas of muted earth tones.