Carbine will be streamlining dye bags so that you can expect to get dyes which match the rarity of the bag, with a small chance to get something better. While in Drop 4, it was possible to receive dyes of lower quality than the bag, in Drop 5 this is no longer possible.
Trunk of Tarnished Tints -> mostly Good dyes (small chance of Excellent or Superb)
Case of Coordinated Colours -> mostly Excellent dyes (small chance of Superb or Legendary)
Duffel Bag of Distinguished Dyes -> mostly Superb dyes (small chance of Legendary)
Pouch of Pristine Pigments -> only Legendary dyes
I don't know whether there will be similar changes to the Shiphand dye bags, but I'd figure there will be.
Right now my dye lists kind of look like they're on crack. I'll be making a fairly large update for Drop 5, but until then, my crazy information is (unfortunately) the closest to accurate we can get (which still isn't terribly accurate at all).
Until Drop 5, I would recommend that you DO NOT PURCHASE Pouch of Pristine Pigments. You may end up very disappointed! Hang on to your gems/renown and save 'em for Drop 5 when you'll be guaranteed something legendary!
Spoiler: Some more detailed resultsShow