#131532

CSS

:root {
  --dark-knight: #131532;
  --dark-knight-rgb: 19 21 50;
  --dark-knight-oklch: oklch(0.212 0.056 277.5);
}

.element {
  color: var(--dark-knight);
  background-color: hsl(236 45% 14%);
  border-color: oklch(0.212 0.056 277.5);
}

Tailwind CSS v4

@theme {
  --color-dark-knight: #131532;
  --color-dark-knight-50: #f1f4ff;
  --color-dark-knight-100: #e3e6fb;
  --color-dark-knight-200: #cfd2ed;
  --color-dark-knight-300: #b1b5d5;
  --color-dark-knight-400: #969cc0;
  --color-dark-knight-500: #7d83ac;
  --color-dark-knight-600: #6a6f91;
  --color-dark-knight-700: #545974;
  --color-dark-knight-800: #3d4156;
  --color-dark-knight-900: #2a2d3c;
  --color-dark-knight-950: #171a26;
}

SCSS

$dark-knight: #131532;
$dark-knight-rgb: 19, 21, 50;
$dark-knight-light: mix(#fff, $dark-knight, 20%);
$dark-knight-dark: mix(#000, $dark-knight, 20%);

.element {
  color: $dark-knight;
  box-shadow: 0 0 0 2px rgba($dark-knight, 0.35);
}