Her existence… it was special for you. That's what yellow meant.
In this song, yellow isn't just one feeling. It's everything he felt for her. His love, his admiration, the way his heart softened whenever he thought of her.
All of that – yellow.
At first, it was the feeling of love quietly blooming in his heart - yellow

Then, even as those feelings grew stronger, he got scared and denied them. But that fear, that mistake… it was yellow too.
Because she was always there. But it was his feelings that made her beautiful in his eyes. His love gave her meaning. And that meaning was yellow. Deep down, he knew what it was. It was love.
He wanted to be there for her, fight for her, protect her, just be with her. Even that desire, that longing, was yellow.
Through his actions, he showed parts of it. But a part of him was still afraid to get too close, so he kept his distance. That fear was yellow too.
"For you, I'd bleed myself dry."
Because he knew – for her, he could do anything.
He decided to fight his fears and insecurities, to become someone who could truly be there for her. Because she was special. She was his yellow.
And even as time goes on, all those feelings – the love, the fear, the hope – they stay alive in his heart. Always yellow.