#03192D

CSS

:root {
  --oxford-by-night: #03192d;
  --oxford-by-night-rgb: 3 25 45;
  --oxford-by-night-oklch: oklch(0.208 0.049 248);
}

.element {
  color: var(--oxford-by-night);
  background-color: hsl(209 88% 9%);
  border-color: oklch(0.208 0.049 248);
}

Tailwind CSS v4

@theme {
  --color-oxford-by-night: #03192d;
  --color-oxford-by-night-50: #ebf7ff;
  --color-oxford-by-night-100: #dceaf8;
  --color-oxford-by-night-200: #c5d6e9;
  --color-oxford-by-night-300: #a5bad0;
  --color-oxford-by-night-400: #88a2bb;
  --color-oxford-by-night-500: #6d8aa6;
  --color-oxford-by-night-600: #5c748c;
  --color-oxford-by-night-700: #495d70;
  --color-oxford-by-night-800: #344453;
  --color-oxford-by-night-900: #242f3a;
  --color-oxford-by-night-950: #131c24;
}

SCSS

$oxford-by-night: #03192d;
$oxford-by-night-rgb: 3, 25, 45;
$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);
}