Ash and Red are suppose to be similar, yet not the same. The anime is much different from the manga.
The biggest indicator is the fact that manga is has much more violence, and is better suited for an older audience. The anime is aimed at a much younger audience, and has more respect for American parent's boundaries.
Not to mention that the producers of Pokémon never said Ash and Red were the same person. There is a reason that they have different names.
Unlike the anime—which, though drawing much inspiration from the games, does not follow them exactly—Pokémon Adventures is a mostly game-based manga, with the fifteen main characters taking their names from the main series games and their various adventures tending to stay restricted to their home region. Also unlike the anime, which has gone to great lengths to indicate the danger of a legendary Pokémon being captured, the main characters of Pokémon Adventures have captured and sometimes use their own legends, much as the player can in the games. Pokémon Adventures also contains darker elements than other media, including certain characters and some Pokémon actually dying.
Snippet from Bulbapedia
Source: I've watched the anime and read the manga.