The recipe book reads that firework stars (small ball single color) are made with a dye and gunpowder, but when you check it, a couple of them aren't consistent. This is what happens when you try and make black or white firework stars:
Expected result: Put in gunpowder and black or white dye and get a firework star!
Bug: Put in gunpowder and either an ink sac or bone meal and get a firework star...
I wouldn't have reported this if cacao beans were part of it too (it would make it seem more intentional) but they aren't, a brown firework star uses brown dye like you'd expect.
Re-testing in 1.20.51, I find that bone meal, ink sac, cocoa beans, and lapis lazuli are all accepted as dyes for making a firework star, so this behavior has now become consistent. I don't think this is the intended behavior, because Java Edition doesn't allow these items to be used as dyes, but we are tracking the parity disagreement as MCPE-42473 so this ticket could be resolved. However, Mojang has not yet closed it internally, so we'll have to keep this ticket open until they do.