Ok, made the following changes:

1. Using same colors as lichess.org now. IIRC blue, green, red and yellow are the arrow colors supported on the website
2. Moved the setting to the new "Theme" screen, this way we can add the shapes to the preview board.
3. Added a colored box to the choice picker entries, although arguably this is now not needed anymore, as the user already gets visual feedback on the preview board.

Great idea to put it in the theme screen! There are some weird conflicts in the game history screen @tom-anders can you see that please?

3. Added a colored box to the choice picker entries, although arguably this is now not needed anymore, as the user already gets visual feedback on the preview board.

It is still useful for iOS users because the picker will be on a different screen.

Another note: I don't think we should return the / blue color in the settings value preview because:

1. it is not that clear this is about the color of the arrow
2. space is constrained on iOS devices and this should be kept short

Another note: I don't think we should return the / blue color in the settings value preview because:

Done!

Also, fixed conflicts now.