The Real Themes of the second OP

Something I've been seeing a lot of just in the comments of pretty much any video for the second opening is the consensus that in the first sequence (the segment of us seeing shots of the world and Momo from Okarun's perspective), Okarun's life was depressing, grey and dull before he met Momo, and that she's his only source of color and energy. This, however, is in my opinion only a portion of the symbolism we were meant to derive, and taking this alone from the opening is actually kind of bad since as much as we all love Okarun and Momo's relationship, we also know it's never healthy to be THAT codependent.

Momo isn't the only thing in Okarun's life that's colorful. No, Momo just HAPPENS to be what Okarun is looking at through his lens, which in the opening have a consistently orange or golden tint. It's not as if Momo herself stands out as yellow and everything else is grey, it's just that she's what he pays attention to about 75% of the time regardless. What's important here is that Okarun's perfectly round glasses are gold, consistent from the previous opening, which is obviously supposed to incite the imagery of his missing balls, the event that kicked off his and Momo's adventures together. Okarun's glasses being gold, then, represents that Momo isn't the source of color in Okarun's life, she's simply the person who showed him that color could exist in the first place, the person who took him on the journey that transformed him from a lonely, self-deprecating wimp to brave and noble protector with a whole family's worth of precious friends, all of whom add their own light to his life. The very next segment supports this when we see said frends, alongside Okarun himself, appear rapidly in distinctive bright colors.

TLDR; Momo isn't the color in Okarun's life, she changed his perspective to help him see it.