#001526

CSS

:root {
  --oxford-by-night: #001526;
  --oxford-by-night-rgb: 0 21 38;
  --oxford-by-night-oklch: oklch(0.188 0.046 243.3);
}

.element {
  color: var(--oxford-by-night);
  background-color: hsl(207 100% 7%);
  border-color: oklch(0.188 0.046 243.3);
}

Tailwind CSS v4

@theme {
  --color-oxford-by-night: #001526;
  --color-oxford-by-night-50: #ebf7ff;
  --color-oxford-by-night-100: #dceaf7;
  --color-oxford-by-night-200: #c5d7e7;
  --color-oxford-by-night-300: #a5bace;
  --color-oxford-by-night-400: #88a2b8;
  --color-oxford-by-night-500: #6c8aa3;
  --color-oxford-by-night-600: #5c7589;
  --color-oxford-by-night-700: #495e6e;
  --color-oxford-by-night-800: #344551;
  --color-oxford-by-night-900: #242f38;
  --color-oxford-by-night-950: #121c23;
}

SCSS

$oxford-by-night: #001526;
$oxford-by-night-rgb: 0, 21, 38;
$oxford-by-night-light: mix(#fff, $oxford-by-night, 20%);
$oxford-by-night-dark: mix(#000, $oxford-by-night, 20%);

.element {
  color: $oxford-by-night;
  box-shadow: 0 0 0 2px rgba($oxford-by-night, 0.35);
}