#120306

CSS

:root {
  --dark-matter: #120306;
  --dark-matter-rgb: 18 3 6;
  --dark-matter-oklch: oklch(0.132 0.033 5.4);
}

.element {
  color: var(--dark-matter);
  background-color: hsl(348 71% 4%);
  border-color: oklch(0.132 0.033 5.4);
}

Tailwind CSS v4

@theme {
  --color-dark-matter: #120306;
  --color-dark-matter-50: #fef1f3;
  --color-dark-matter-100: #f3e4e6;
  --color-dark-matter-200: #e2cfd2;
  --color-dark-matter-300: #c7b1b4;
  --color-dark-matter-400: #b1979b;
  --color-dark-matter-500: #9a7d83;
  --color-dark-matter-600: #826a6f;
  --color-dark-matter-700: #685559;
  --color-dark-matter-800: #4d3e41;
  --color-dark-matter-900: #352a2d;
  --color-dark-matter-950: #20181a;
}

SCSS

$dark-matter: #120306;
$dark-matter-rgb: 18, 3, 6;
$dark-matter-light: mix(#fff, $dark-matter, 20%);
$dark-matter-dark: mix(#000, $dark-matter, 20%);

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