#673900

CSS

:root {
  --brown: #673900;
  --brown-rgb: 103 57 0;
  --brown-oklch: oklch(0.393 0.09 62.7);
}

.element {
  color: var(--brown);
  background-color: hsl(33 100% 20%);
  border-color: oklch(0.393 0.09 62.7);
}

Tailwind CSS v4

@theme {
  --color-brown: #673900;
  --color-brown-50: #fff1db;
  --color-brown-100: #fee2c9;
  --color-brown-200: #f0cdad;
  --color-brown-300: #d8ae87;
  --color-brown-400: #c59366;
  --color-brown-500: #b07843;
  --color-brown-600: #95663a;
  --color-brown-700: #78512e;
  --color-brown-800: #593b20;
  --color-brown-900: #3e2815;
  --color-brown-950: #271607;
}

SCSS

$brown: #673900;
$brown-rgb: 103, 57, 0;
$brown-light: mix(#fff, $brown, 20%);
$brown-dark: mix(#000, $brown, 20%);

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