Iri said:
Siver = Gray's embittered kid from the future who grew up seeing his dad going down to the guild nightly and getting drunk with his friend Natsu rather than properly raising his own son and showering love on his beautiful wife, Juvia. After one night seeing his dad drag himself in, drooling and stark naked, he snaps: "Dammit, I'm going to go back in time and fix this using whatever Future Rogue did in Chapter 324. I bet I'm even one of the future people Arcadios mentioned on page 5!"
Remember, blue+gray=silver. Actually, it probably doesn't, but it sounds catchy.
So silver is Trunks.