#061015

CSS

:root {
  --black-knight: #061015;
  --black-knight-rgb: 6 16 21;
  --black-knight-oklch: oklch(0.166 0.019 229.7);
}

.element {
  color: var(--black-knight);
  background-color: hsl(200 56% 5%);
  border-color: oklch(0.166 0.019 229.7);
}

Tailwind CSS v4

@theme {
  --color-black-knight: #061015;
  --color-black-knight-50: #f0f6fa;
  --color-black-knight-100: #e2e9ed;
  --color-black-knight-200: #cdd6db;
  --color-black-knight-300: #aeb9bf;
  --color-black-knight-400: #94a1a7;
  --color-black-knight-500: #7a8990;
  --color-black-knight-600: #67747a;
  --color-black-knight-700: #535d62;
  --color-black-knight-800: #3c4448;
  --color-black-knight-900: #292f32;
  --color-black-knight-950: #171b1e;
}

SCSS

$black-knight: #061015;
$black-knight-rgb: 6, 16, 21;
$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);
}