#00182B

CSS

:root {
  --oxford-by-night: #00182b;
  --oxford-by-night-rgb: 0 24 43;
  --oxford-by-night-oklch: oklch(0.201 0.05 244);
}

.element {
  color: var(--oxford-by-night);
  background-color: hsl(207 100% 8%);
  border-color: oklch(0.201 0.05 244);
}

Tailwind CSS v4

@theme {
  --color-oxford-by-night: #00182b;
  --color-oxford-by-night-50: #eaf7ff;
  --color-oxford-by-night-100: #dbeaf8;
  --color-oxford-by-night-200: #c4d7e9;
  --color-oxford-by-night-300: #a3bbd0;
  --color-oxford-by-night-400: #86a2ba;
  --color-oxford-by-night-500: #6a8aa5;
  --color-oxford-by-night-600: #5a758c;
  --color-oxford-by-night-700: #485e70;
  --color-oxford-by-night-800: #334552;
  --color-oxford-by-night-900: #233039;
  --color-oxford-by-night-950: #121c24;
}

SCSS

$oxford-by-night: #00182b;
$oxford-by-night-rgb: 0, 24, 43;
$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);
}