The mystery has been solved! Yes, that is how the developer drop should appear.
As far as bottles are concerned, I recommend bottled sparkling water bottles from the grocery store that have plastic (not foil) caps.
You will, of course, need to drink the sparkling water first.
If you get two different types, it will be easier to differentiate them at a glance.
In any event, mark them very, very clearly with their contents!
Coloured bottles are nice, but they can make it harder to examine the contents.
It is a good idea to store them away from bright light.
By the way, I'd also recommend buying at least two packages of everything. That way you can replenish your stock at leisure when you use the last package/bottle in your inventory.