My guess is that Red being silent in games like GSC and HGSS is like an allusion to the Kanto games, where you play as Red and therefore don't really have any lines of dialogue. The Gen 2 games are basically sequels to Gen 1 and the point the devs were trying to get across is that the Red NPC you fight as Gold is, in canon, the same person you played in the Kanto games. But I guess this doesn't apply to anime, I think Red talked in Pokemon Origins.