#6C3800

CSS

:root {
  --brown: #6c3800;
  --brown-rgb: 108 56 0;
  --brown-oklch: oklch(0.399 0.095 58.4);
}

.element {
  color: var(--brown);
  background-color: hsl(31 100% 21%);
  border-color: oklch(0.399 0.095 58.4);
}

Tailwind CSS v4

@theme {
  --color-brown: #6c3800;
  --color-brown-50: #fff0da;
  --color-brown-100: #ffe1c9;
  --color-brown-200: #f3ccac;
  --color-brown-300: #dcad86;
  --color-brown-400: #c99065;
  --color-brown-500: #b57542;
  --color-brown-600: #996438;
  --color-brown-700: #7b502d;
  --color-brown-800: #5b3920;
  --color-brown-900: #402715;
  --color-brown-950: #291507;
}

SCSS

$brown: #6c3800;
$brown-rgb: 108, 56, 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);
}