Soulmark Hand Prints (слэш)

Everyone is born with their soulmate's handprint on the back of their neck, and when it is touched by the person it belongs to, it changes color or causes a sensation. Both, sometimes.
Steve's is green, always has been. The normal sized hand of a child about his age. The size, Bucky thinks, of his hand.
But Bucky's is big and blue, a grown man's hand. It wraps around the back of his neck to dip over his shoulders towards his collarbone. Much too large to be Steve's.
It's not enough to stop him loving Steve, but his best friend won't hear a word of it, won't even allow them to discuss it. Then there’s the draft and Project Rebirth, and Steve is bigger but doesn’t think about it. He goes to save Bucky and Bucky is mad as hell at the risk he took, the dumb punk, and also relieved and stubborn because--
Steve's hands are a lot bigger now.