Lumen's patient portal is used at 3am by nurses and patients. Light mode was causing fatigue and headaches. We interviewed the patient council, defined a semantic token layer for light/dark, and rebuilt the portal shell with prefers-color-scheme support and manual toggle with persistence.
Every component was audited for contrast, focus order and reduced motion. axe-core runs in CI now. Adoption hit 67% in two weeks, night-shift NPS rose 11 points, and the audit helped Lumen meet its compliance deadline a month early.