The rules specify otherwise, the player can usually return after serving the designated penalty time, even if the opposing team scores during that time.
In most cases in sports like soccer, receiving a blue card usually indicates a temporary expulsion from the game, often for a certain duration like a few minutes.
The player typically has to leave the field for that period and can return once the penalty time is up or when allowed by the rules of the sport.
So, unless the rules specify otherwise, the player can usually return after serving the designated penalty time, even if the opposing team scores during that time.