#011325

CSS

:root {
  --oxford-by-night: #011325;
  --oxford-by-night-rgb: 1 19 37;
  --oxford-by-night-oklch: oklch(0.182 0.046 247.8);
}

.element {
  color: var(--oxford-by-night);
  background-color: hsl(210 95% 7%);
  border-color: oklch(0.182 0.046 247.8);
}

Tailwind CSS v4

@theme {
  --color-oxford-by-night: #011325;
  --color-oxford-by-night-50: #ecf7ff;
  --color-oxford-by-night-100: #dde9f7;
  --color-oxford-by-night-200: #c6d6e8;
  --color-oxford-by-night-300: #a6bace;
  --color-oxford-by-night-400: #8aa1b9;
  --color-oxford-by-night-500: #6e89a4;
  --color-oxford-by-night-600: #5e748a;
  --color-oxford-by-night-700: #4b5d6f;
  --color-oxford-by-night-800: #354451;
  --color-oxford-by-night-900: #242f39;
  --color-oxford-by-night-950: #131c23;
}

SCSS

$oxford-by-night: #011325;
$oxford-by-night-rgb: 1, 19, 37;
$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);
}