Why do some Pokemon cards have the HP number printed red instead of black?

You're likely thinking of Pokémon cards with red HP numbers indicating they have a Weakness to the corresponding type.

Here's how it works:

* Black HP: This is the standard HP number found on most Pokémon cards.

* Red HP: This indicates that the Pokémon is weak to the type represented by the color of the HP number. For example, a Pokémon with red HP is weak to Fire-type attacks.

This visual cue helps players quickly identify a Pokémon's weaknesses during battles, making the game more strategic.

It's worth noting that this is a common practice in Pokémon trading card games, but some older sets may not have this feature.