Give the Dex interface more color — accent colors or a brighter theme

Let people add more color to the Dex interface — an accent color, or a theme with more contrast between areas of the screen.

Current gap: The web app ships Light, Dark and System themes and nothing else. There is no accent color and no way to give parts of the screen their own color, so a user who finds the default palette flat has no setting to reach for.

Desired outcome:

• An accent color choice that carries through buttons, highlights and selected rows.

• More visual separation between regions of the screen, so the layout reads at a glance.

• Keep the current look available as the default for people who prefer it.