Apologies. I misinterpreted based on your statement the store was a liquidator. I assumed perhaps the darker product was older stock.
Yes, depending on size and type of container, often coloration occurs from outside in, but eventually the entire product darkens. This based on my experience with stuff left on the shelf for many years. Back in the day, vaseline was packaged in tin cans which blocked UV and same darkening still occurred, so I assume it has more to do with oxidation and possibly loss of volatiles? The smell changes over time too. (Bag Balm currently packaged in tin cans and same occurs with it).
I know nothing about how petroleum jelly is manufactured/refined. Question about what can be inferred from color was honest/innocent, not intended as judgmental/critical.
Edit: So, in the quest to answer my own curiosity reference product color differences I found this:
"The substance consists of saturated hydrocarbons with carbon numbers mainly higher than 25.
Its composition depends upon the petroleum source and refining process.
Highly refined (White Petrolatum) grades are used in pharmacy and cosmetics.
Less refined grades (Yellow, amber or brown Petrolatum) are used industrially and may contain impurities such as carcinogenic polycyclic aromatics."
and this:
http://www.kerasalpro.com/resources/key-ingredients/petrolatum-pharmaceuticalexcipients.pdf
So, I've learned that petrolatum is a variable hydrocarbon mixture, not a compound; may contain stabilizers/antioxidants; and color is dependent upon source ingredients and degree of refinement... All vaseline is not the same. (And it darkens with age).