Viridian is Viridian.
(I assume Viridian's genderless. And only best friends with Vermil{l}[ion].)
And I also assume Viridian is genderless, and Vermilion and Verdigris are friends with each other and him. I think Verdigris, because he's willing to talk to Viridian about being in love.... Only friends do that.
EDIT: Explanation.
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as Best friends.