#B99467

CSS

:root {
  --cardboard: #b99467;
  --cardboard-rgb: 185 148 103;
  --cardboard-oklch: oklch(0.69 0.075 71.5);
}

.element {
  color: var(--cardboard);
  background-color: hsl(33 37% 56%);
  border-color: oklch(0.69 0.075 71.5);
}

Tailwind CSS v4

@theme {
  --color-cardboard: #b99467;
  --color-cardboard-50: #fff2de;
  --color-cardboard-100: #f8e5cd;
  --color-cardboard-200: #e8d0b1;
  --color-cardboard-300: #cfb28d;
  --color-cardboard-400: #bb976d;
  --color-cardboard-500: #a57e4c;
  --color-cardboard-600: #8c6b41;
  --color-cardboard-700: #705534;
  --color-cardboard-800: #533e25;
  --color-cardboard-900: #3a2a18;
  --color-cardboard-950: #241809;
}

SCSS

$cardboard: #b99467;
$cardboard-rgb: 185, 148, 103;
$cardboard-light: mix(#fff, $cardboard, 20%);
$cardboard-dark: mix(#000, $cardboard, 20%);

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