#001118

CSS

:root {
  --black-knight: #001118;
  --black-knight-rgb: 0 17 24;
  --black-knight-oklch: oklch(0.165 0.031 223.4);
}

.element {
  color: var(--black-knight);
  background-color: hsl(198 100% 5%);
  border-color: oklch(0.165 0.031 223.4);
}

Tailwind CSS v4

@theme {
  --color-black-knight: #001118;
  --color-black-knight-50: #ecf7fc;
  --color-black-knight-100: #deeaf0;
  --color-black-knight-200: #c7d7de;
  --color-black-knight-300: #a8bbc3;
  --color-black-knight-400: #8ca3ac;
  --color-black-knight-500: #718b95;
  --color-black-knight-600: #5f767e;
  --color-black-knight-700: #4c5e65;
  --color-black-knight-800: #37454a;
  --color-black-knight-900: #263033;
  --color-black-knight-950: #141c1f;
}

SCSS

$black-knight: #001118;
$black-knight-rgb: 0, 17, 24;
$black-knight-light: mix(#fff, $black-knight, 20%);
$black-knight-dark: mix(#000, $black-knight, 20%);

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