Mozilla's design system for Firefox surfaces: system fonts at a 15px root, near-black #15141a ink on white with the lavender-tinted gray ramp (#f0f0f4, #bfbfc9, #1c1b22), a vivid blue accent that becomes cyan in dark mode, 4/8px radii, soft layered shadows, and tokens engineered around light-dark() pairs, prefers-contrast, and forced-colors modes.
Primary actionThe dark-mode accent swap: interactive blue (blue-60) becomes bright cyan (cyan-30) on Firefox's #1c1b22 charcoal — links, focus rings, and primary buttons all pivot hue rather than merely lightening.