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No, if the toxin effected the breath then it's toxic, we went through this before, it's extremely virulent.
Furthermore, any coloring has to be some sort of mechanism intended for that. To achieve enough of a concentration to recolor the air means a large amount of whatever substance that can't be attributed to natural breathing unless it's a evolutionary mechanism intended to put that there. Basically either it's body toxifies the exhale or it's the byproduct of their breathing (like CO2 for our breathing, though I assume they store some of it if so).
Again, the major issue there is that they have something to use it with, furthermore, it's far too much evolutionary dedication to just be a show unless it helps with mating.
There's also the fact that the white pikmin are basically brimming with poison (periphials deal damage and are instant death to enemies), their breath would be poisonious regardless, just to a lower extent.
Overall, that makes it near evolutionarily impossible for it to just be a show. Markings (which it has) are a lot more practical for this type of situation, it's already dangerious to eat after all. There's no evolutionary reason for it to have "hey look at me, I'm poisonious" breath as well.
edit:
You realize my argument is not that it does that in the game, but that it's unrealistic for it to not act in the manner which I'm talking about?