Red and Blue had the same graphics outside of Japan. People seeing these boxes weren't choosing between sprite work.

In fact, going by the Japanese versions, it was Blue that we never got. Red and Blue outside of Japan were just reskinned Red and Green.

Hence why one of the trainers being able to talk about the Raichu that you traded him evolving -- it came from the script of the wrong version of the game (I'm guessing Blue) even though the games have the Red/Green trades (I think).

You might have known this, but adding for clarity that the west still got Red/Green under the hood but with Blue's sprites shared between both games.