Every color here comes from CSS --apx-* tokens (--apx-accent, --apx-fore, --apx-grid, --apx-surface) defined once in the stylesheet. The chart config sets no colors at all. The first button flips a class that swaps the token values; with theme: { follow: 'os' } the chart also tracks the OS prefers-color-scheme automatically, no JS required. Shuffle accent token changes only the CSS variable at runtime and calls chart.refreshTokens(), which re-reads the cascade and re-renders: the path for design-system theme switches that are not an OS color-scheme flip.