You can change a habit's icon and color anytime, and your streak isn't affected.
- On the Today screen, tap the habit to open its details.
- Tap Edit (the pencil at the top).
- Under Icon, pick one of 12 icons: book, water, walking, language, workout, code, meditation, sleep, writing, music, health or morning.
- Under Color, pick orange, blue, green, purple, pink or teal.
- Check the Preview to see how the card will look, then tap Save.
The new look shows up everywhere the habit appears, including the Today list and your stats.
Every icon and color is free. The app's overall look, Light, Dark or System, is a separate setting under Profile › Settings › Theme, and that's free too.