#031524

CSS

:root {
  --oxford-by-night: #031524;
  --oxford-by-night-rgb: 3 21 36;
  --oxford-by-night-oklch: oklch(0.189 0.04 244.7);
}

.element {
  color: var(--oxford-by-night);
  background-color: hsl(207 85% 8%);
  border-color: oklch(0.189 0.04 244.7);
}

Tailwind CSS v4

@theme {
  --color-oxford-by-night: #031524;
  --color-oxford-by-night-50: #ecf7ff;
  --color-oxford-by-night-100: #deeaf5;
  --color-oxford-by-night-200: #c7d6e5;
  --color-oxford-by-night-300: #a8bacb;
  --color-oxford-by-night-400: #8ba1b5;
  --color-oxford-by-night-500: #70899f;
  --color-oxford-by-night-600: #5f7487;
  --color-oxford-by-night-700: #4c5d6c;
  --color-oxford-by-night-800: #37444f;
  --color-oxford-by-night-900: #252f37;
  --color-oxford-by-night-950: #141c22;
}

SCSS

$oxford-by-night: #031524;
$oxford-by-night-rgb: 3, 21, 36;
$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);
}