#816754

CSS

:root {
  --pastel-brown: #816754;
  --pastel-brown-rgb: 129 103 84;
  --pastel-brown-oklch: oklch(0.534 0.044 57.8);
}

.element {
  color: var(--pastel-brown);
  background-color: hsl(25 21% 42%);
  border-color: oklch(0.534 0.044 57.8);
}

Tailwind CSS v4

@theme {
  --color-pastel-brown: #816754;
  --color-pastel-brown-50: #fff3e9;
  --color-pastel-brown-100: #f3e5da;
  --color-pastel-brown-200: #e3d0c2;
  --color-pastel-brown-300: #c9b3a1;
  --color-pastel-brown-400: #b39985;
  --color-pastel-brown-500: #9d7f6a;
  --color-pastel-brown-600: #856c5a;
  --color-pastel-brown-700: #6a5648;
  --color-pastel-brown-800: #4f3f34;
  --color-pastel-brown-900: #372b23;
  --color-pastel-brown-950: #221812;
}

SCSS

$pastel-brown: #816754;
$pastel-brown-rgb: 129, 103, 84;
$pastel-brown-light: mix(#fff, $pastel-brown, 20%);
$pastel-brown-dark: mix(#000, $pastel-brown, 20%);

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