adverbs - Is this an adjective or a noun?

(1) Dotted here and there among the students, the ghosts shone misty silver.
(2) Then the hat twitched. A rip near the brim opened wide like a mouth - and the hat began to sing:
(Harry Potter and the Sorcerer's Stone)

Is the ‘misty silver’ a predicative adjective that denote the result of the intransitive verb like in the second example? Or is it an object of the transitive verb?

Answer

Oh, dear. This sort of thing is where ordinary part-of-speech and sentence-constituent analysis gets very iffy.

The actual meaning is perfectly clear:

The ghosts shone in such a manner that they looked misty silver.
The rip opened like a mouth. The opening was wide.

If you like to call the pair of adjectives misty silver (in which misty modifies silver) a secondary complement, that's cool; it gives you a name which tells you how it works.

But you can't do that with wide, because wide taken as an adjective wouldn't modify an entity present in the sentence, rip or mouth, but the implicit opening created. This is just how wide works. The simplest way of analyzing it is as an adverb on open; that's how OED treats it. It's very old in that sense, like hard, predating the practice of forming adverbs with the -ly suffix; and also like hard it has a doublet which does have the -ly suffix and which bears a slightly different meaning.