#05192A

CSS

:root {
  --oxford-by-night: #05192a;
  --oxford-by-night-rgb: 5 25 42;
  --oxford-by-night-oklch: oklch(0.207 0.043 246.5);
}

.element {
  color: var(--oxford-by-night);
  background-color: hsl(208 79% 9%);
  border-color: oklch(0.207 0.043 246.5);
}

Tailwind CSS v4

@theme {
  --color-oxford-by-night: #05192a;
  --color-oxford-by-night-50: #ecf7ff;
  --color-oxford-by-night-100: #ddeaf6;
  --color-oxford-by-night-200: #c7d6e6;
  --color-oxford-by-night-300: #a7bacd;
  --color-oxford-by-night-400: #8aa1b7;
  --color-oxford-by-night-500: #6f89a2;
  --color-oxford-by-night-600: #5e7489;
  --color-oxford-by-night-700: #4b5d6d;
  --color-oxford-by-night-800: #364450;
  --color-oxford-by-night-900: #252f38;
  --color-oxford-by-night-950: #131c23;
}

SCSS

$oxford-by-night: #05192a;
$oxford-by-night-rgb: 5, 25, 42;
$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);
}