The speaker is wrestling with the feeling of not fitting any label. The opening lines swap two ideas: glittering looks with dark souls, then dark looks with glittering souls. Both are called "a trend," which suggests that these images of shine and shadow are things people put on, a kind of fashion, rather than anything deeply true.
That's why the next two stanzas feel so uneasy. When glitter is everywhere, or darkness is everywhere, it becomes hard to tell what's genuine, especially since "shades" of each keep shifting. The repetition, with the words flipped, makes the confusion feel like a loop the speaker can't escape.
The last stanza lands on a quiet realization. Choosing the "right shade" of either one is pointless, because the speaker is neither. The closing phrase, "glittering darkness," joins the opposites into one identity. The mood is tired and searching, but there's a small relief at the end: the speaker stops sorting themselves into boxes and accepts being both at once.