Well, the Color of the various Plasma bolts reveals the Chemical Makeup of the ammunition that is flashed into Plasma.
There are a number of possible choices.
Various "generations" of plasma weapons would have tried out different compounds, just as our own current weapons use everything from solid lead, to brass jacketed lead, to spent Uranium depending on just what the particular ammo was intended to do and to what sort of Target it was designed for.
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Do not ascribe your own motivations to others:
At best, it will break your heart.
At worst, it will get you dead."