The Italian stamps are Scott 88; 1.25l blue & ultramarine issued in 1926
In Scott, the colors are listed from the frame inward so, the dark frame and portrait is blue while the wreath around the portrait is ultramarine.
I suspect that the intensity of the ultramarine varied during printing - The color is there on all of our examples.
For these stamps to be errors, the ultramarine would have to be completely missing - even under a microscope.
Another possible kind of error would be for a color other than ultramarine being used, but these examples do not seem to be different colors.