#643A00

CSS

:root {
  --brown: #643a00;
  --brown-rgb: 100 58 0;
  --brown-oklch: oklch(0.391 0.087 66);
}

.element {
  color: var(--brown);
  background-color: hsl(35 100% 20%);
  border-color: oklch(0.391 0.087 66);
}

Tailwind CSS v4

@theme {
  --color-brown: #643a00;
  --color-brown-50: #fff1db;
  --color-brown-100: #fce3ca;
  --color-brown-200: #eecead;
  --color-brown-300: #d6b088;
  --color-brown-400: #c29466;
  --color-brown-500: #ad7a43;
  --color-brown-600: #92673a;
  --color-brown-700: #75532e;
  --color-brown-800: #573c20;
  --color-brown-900: #3d2915;
  --color-brown-950: #261707;
}

SCSS

$brown: #643a00;
$brown-rgb: 100, 58, 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);
}