It's good that Prologue Quests now give a popup when you start them to warn you that you've started one, but I think that could be improved further if they actually have a unique icon.
The Normal Quest icon is this one:
and the Zone Story icon is this one:
.
My suggestion would be to use something like this for Prologue Quests:
It's an existing icon which is currently (mis-)used as the Zone Story icon in a few loading screens; if that was corrected to the true Zone Story icon (above), this one would be unused. It's different enough from the Normal Quest icon to get you to think about what it is, but not so different that it looks completely out-of-place. Meanwhile I think it looks a bit like "a quest pointing to another quest", which is essentially what a Prologue Quest already is.
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