#01141E

CSS

:root {
  --black-knight: #01141e;
  --black-knight-rgb: 1 20 30;
  --black-knight-oklch: oklch(0.18 0.034 231.7);
}

.element {
  color: var(--black-knight);
  background-color: hsl(201 94% 6%);
  border-color: oklch(0.18 0.034 231.7);
}

Tailwind CSS v4

@theme {
  --color-black-knight: #01141e;
  --color-black-knight-50: #ecf7fe;
  --color-black-knight-100: #ddeaf2;
  --color-black-knight-200: #c7d7e1;
  --color-black-knight-300: #a7bbc7;
  --color-black-knight-400: #8ba3af;
  --color-black-knight-500: #708b99;
  --color-black-knight-600: #5f7582;
  --color-black-knight-700: #4c5e68;
  --color-black-knight-800: #36454c;
  --color-black-knight-900: #253035;
  --color-black-knight-950: #141c20;
}

SCSS

$black-knight: #01141e;
$black-knight-rgb: 1, 20, 30;
$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);
}