#01111A

CSS

:root {
  --black-knight: #01111a;
  --black-knight-rgb: 1 17 26;
  --black-knight-oklch: oklch(0.167 0.032 231.7);
}

.element {
  color: var(--black-knight);
  background-color: hsl(202 93% 5%);
  border-color: oklch(0.167 0.032 231.7);
}

Tailwind CSS v4

@theme {
  --color-black-knight: #01111a;
  --color-black-knight-50: #edf7fd;
  --color-black-knight-100: #deeaf1;
  --color-black-knight-200: #c8d7e0;
  --color-black-knight-300: #a8bbc5;
  --color-black-knight-400: #8ca2ae;
  --color-black-knight-500: #728a98;
  --color-black-knight-600: #607580;
  --color-black-knight-700: #4d5e67;
  --color-black-knight-800: #37454b;
  --color-black-knight-900: #262f34;
  --color-black-knight-950: #141c20;
}

SCSS

$black-knight: #01111a;
$black-knight-rgb: 1, 17, 26;
$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);
}