1948 Bowman Color Variation

[STL1944]

Question for the group.... One of the sets that I am trying to complete is a raw version of the 1948 Bowman. I like the cards as the first recognized post-war set (although I like the 1947 Tip Top Bread cards as well) and has some good names in only 48 cards.

What I don't like is the color. Not that the site is in black and white, but the variation in the color of the stock paper/cardboard on which the cards are printed. They seem to vary from off-white to almost a light brown.

(see images below)

In looking at some of the cards that I have obtained, some of them look nice and other just look "dirty".

In scouting email today, I came across the following cards. (see images) Note where the thumbtack use to be. Notice how white that part of the card is next to the "brown background" of the "exposed" portion of the card:

This makes me wonder: was there all that amount of color variation in the card stock or was there less variation in the stock and more due to the ravages of age?

Note: I do not see this issue with my 1953 Bowman Black and Whites....

Thoughts?