So about a year ago I bought a LV Flamingo Hilton $5 chip that was a brown color and became convinced that it was a discolored red $5 chip. Here are the two chips.

Then today I spot this auction for a $25 LV Flamingo Hilton chip
https://www.reviewjournal.com/sports/golf/historic-las-vegas-country-club-sale-process-ends-this-week/
Here is the chip from my collection and an image of the chip in the auction


Doesn't it seem odd that only these two chips have radically changed color and I've not seen this change in any other chips. Any ideas?