The answer:
Ditto is purple.
How do we know?
- Official Artwork: The official artwork for Ditto, including the Pokémon Trading Card Game, consistently depicts Ditto as purple.
- In-game Appearance: In all Pokémon video games, Ditto appears in its signature purple form.
- Anime Series: The anime series also consistently portrays Ditto as purple.
While Ditto can transform into different colors, its natural form is purple.
