The canasta decks did come in an older and newer version - the older version was available in two colors, red and blue, while the newer just comes in one (I think red). You actually need two 52-card decks to make a single canasta deck.
If I had to guess, I'd say your package you spotted on eBay is the older of the two listed. I recently bought the newer one. The contents of the boxes could be completely identical, however - they could be two different packagings for the same version of the two-deck set.