What is your interpretation of the the Necklace and what it means for Timebomb's future?

At first I was only focused on the blue aspect of the necklace because it's the most prominent color and outlines Ekko more then Jinx. Blue roses signify an "Impossible or Unattainable love that can't be present in reality".

Now at first it would be easy to assume that this signifies that Ekko sees his love for Jinx as something beyond reach, unattainable in his reality and only able to be present in a reality far removed from his, a dream like reality if you would.

White roses represent innocence, purity and marriage, AU Powder is placed next to Ekko and she represents that. Now obviously Ekko and Powder aren't married, so you can assume that its more of another way of defining their relationship.

But white roses as well as blue roses also represent New Beginnings, Ekko tells Jinx that she can build something new and follows that up by telling Jinx "Someone worth building it for". Now my personal interpretation of this, is that. That part is Ekko saying that despite his love for her feeling like it might be unattainable, he still wants to try building something new (a new and better Zaun for his and her people) because she's his reason. Conversely and judging by the Artbook, it's not out of the realm of possibility that Jinx has feelings for Ekko and the new home she found with Ekko and the Firelights and she said that she'd be back.

So for now I believe that their love is unattainable, but that's solely because their environment won't allow for them to both be together in a way that they can build something together in a healthier and safe way, the way their AU counterparts built their relationship.