#673700

CSS

:root {
  --brown: #673700;
  --brown-rgb: 103 55 0;
  --brown-oklch: oklch(0.389 0.091 60.5);
}

.element {
  color: var(--brown);
  background-color: hsl(32 100% 20%);
  border-color: oklch(0.389 0.091 60.5);
}

Tailwind CSS v4

@theme {
  --color-brown: #673700;
  --color-brown-50: #fff0db;
  --color-brown-100: #ffe2ca;
  --color-brown-200: #f1ccad;
  --color-brown-300: #daae87;
  --color-brown-400: #c69266;
  --color-brown-500: #b27744;
  --color-brown-600: #96653a;
  --color-brown-700: #79512e;
  --color-brown-800: #5a3a21;
  --color-brown-900: #3f2816;
  --color-brown-950: #281607;
}

SCSS

$brown: #673700;
$brown-rgb: 103, 55, 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);
}