#040400

CSS

:root {
  --black-metal: #040400;
  --black-metal-rgb: 4 4 0;
  --black-metal-oklch: oklch(0.103 0.023 109.8);
}

.element {
  color: var(--black-metal);
  background-color: hsl(60 100% 1%);
  border-color: oklch(0.103 0.023 109.8);
}

Tailwind CSS v4

@theme {
  --color-black-metal: #040400;
  --color-black-metal-50: #f5f6ef;
  --color-black-metal-100: #e8e9e0;
  --color-black-metal-200: #d4d5cb;
  --color-black-metal-300: #b7b9ac;
  --color-black-metal-400: #9fa091;
  --color-black-metal-500: #878877;
  --color-black-metal-600: #727365;
  --color-black-metal-700: #5b5c50;
  --color-black-metal-800: #43433a;
  --color-black-metal-900: #2e2e28;
  --color-black-metal-950: #1b1b16;
}

SCSS

$black-metal: #040400;
$black-metal-rgb: 4, 4, 0;
$black-metal-light: mix(#fff, $black-metal, 20%);
$black-metal-dark: mix(#000, $black-metal, 20%);

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