Odd, on my monitor they all appear to have a slight tint to the backgrounds.
A couple thoughts on fading.
The black ink from that era usually won't fade. The inks would have been some degree of carbonblack in an oil with maybe a touch of something like zinc oxide to make it more opaque. (And slightly gray since zinc oxide is white)
Some reds fade terribly. Some are so bad they'll fade entirely away. Unfortunately red was also an expensive color and there were many formulations all of which were kept a bit secret. Some faded quickly, others were nearly permanent.
They do look like either a missed color or more likely to my mind with two showing some color a different printing error.
Most likely is a mistake I'll call a secondary print. (I'll find the correct technical term eventually)
The ink rollers can be lifted from the plate/stone, usually something that's done to clean the press. Since not all of the ink transfers from the rubber roller that picks it up off the plate if another sheet runs through the press it will get a weak impression.
Steve B
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