#002237

CSS

:root {
  --oxford-by-night: #002237;
  --oxford-by-night-rgb: 0 34 55;
  --oxford-by-night-oklch: oklch(0.241 0.056 240.6);
}

.element {
  color: var(--oxford-by-night);
  background-color: hsl(203 100% 11%);
  border-color: oklch(0.241 0.056 240.6);
}

Tailwind CSS v4

@theme {
  --color-oxford-by-night: #002237;
  --color-oxford-by-night-50: #e8f8ff;
  --color-oxford-by-night-100: #d9ebf9;
  --color-oxford-by-night-200: #c0d8eb;
  --color-oxford-by-night-300: #9fbbd2;
  --color-oxford-by-night-400: #81a3bd;
  --color-oxford-by-night-500: #648ba8;
  --color-oxford-by-night-600: #55768e;
  --color-oxford-by-night-700: #445e72;
  --color-oxford-by-night-800: #304554;
  --color-oxford-by-night-900: #21303a;
  --color-oxford-by-night-950: #101c24;
}

SCSS

$oxford-by-night: #002237;
$oxford-by-night-rgb: 0, 34, 55;
$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);
}