#00192B

CSS

:root {
  --oxford-by-night: #00192b;
  --oxford-by-night-rgb: 0 25 43;
  --oxford-by-night-oklch: oklch(0.204 0.049 242);
}

.element {
  color: var(--oxford-by-night);
  background-color: hsl(205 100% 8%);
  border-color: oklch(0.204 0.049 242);
}

Tailwind CSS v4

@theme {
  --color-oxford-by-night: #00192b;
  --color-oxford-by-night-50: #eaf7ff;
  --color-oxford-by-night-100: #dbeaf7;
  --color-oxford-by-night-200: #c3d7e8;
  --color-oxford-by-night-300: #a3bbcf;
  --color-oxford-by-night-400: #86a3b9;
  --color-oxford-by-night-500: #6a8ba4;
  --color-oxford-by-night-600: #5a758b;
  --color-oxford-by-night-700: #485e6f;
  --color-oxford-by-night-800: #334552;
  --color-oxford-by-night-900: #233039;
  --color-oxford-by-night-950: #121c23;
}

SCSS

$oxford-by-night: #00192b;
$oxford-by-night-rgb: 0, 25, 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);
}