So I happened on this current eBay auction for a sealed Millennium Edition HC set, and my first thought was that the spines were sun faded:

Seller: allthingstrading
Ended May 17, 2022
[4 Bids]
Submitted by: Witchking664

The seller says it’s a “white” (rather than red) colouration version, but this is the first time I’ve ever seen one like this.