There are definitely cards that are missing color passes and I am not saying that there aren't. And T206 inks weren't always mixed the same either - probably the most famous examples of this are the Hindu red background portraits that are actually red-orange. However, those cards are red-orange with strong colors throughout the card.
On T206, the red ink is the "weakest" - it is the first to change when a card is faded or exposed to chemicals. Black is the most resistant and stays fine through a lot of punishment. The fact that the yellow along the left border fades from top to bottom at the same point the red does makes this a pretty rock solid case of fading. I think all of the colors on both of these Cobbs (minus the red strip at the top of Burdick's) are a bit washed out (though unevenly watched out, as the colors don't fade at the same rate), which suggests sun exposure.
Here are more examples of cards that the sun has washed out only parts of and which are not print goofs. One Cobb clearly shows the outline of an album hinge on the corner. The other Cobb shows that there was something that covered the top and a sliver of the right side, though some light still was able to get under it. The others either had some sort of a clip, tape, or something else that protected that one section and made it fade slower than the rest.
Cobb scrapbook holder.JPG
Cobb partly faded.JPG
Burke sun a.jpg
Tape 2.1.jpg