#003D3E

CSS

:root {
  --rich-black: #003d3e;
  --rich-black-rgb: 0 61 62;
  --rich-black-oklch: oklch(0.326 0.056 196.6);
}

.element {
  color: var(--rich-black);
  background-color: hsl(181 100% 12%);
  border-color: oklch(0.326 0.056 196.6);
}

Tailwind CSS v4

@theme {
  --color-rich-black: #003d3e;
  --color-rich-black-50: #e4fafb;
  --color-rich-black-100: #d4eeef;
  --color-rich-black-200: #badcdd;
  --color-rich-black-300: #97c1c2;
  --color-rich-black-400: #77a9a9;
  --color-rich-black-500: #589293;
  --color-rich-black-600: #4b7b7c;
  --color-rich-black-700: #3b6363;
  --color-rich-black-800: #2a4948;
  --color-rich-black-900: #1c3232;
  --color-rich-black-950: #0c1e1e;
}

SCSS

$rich-black: #003d3e;
$rich-black-rgb: 0, 61, 62;
$rich-black-light: mix(#fff, $rich-black, 20%);
$rich-black-dark: mix(#000, $rich-black, 20%);

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