#816751

CSS

:root {
  --pastel-brown: #816751;
  --pastel-brown-rgb: 129 103 81;
  --pastel-brown-oklch: oklch(0.534 0.047 61.8);
}

.element {
  color: var(--pastel-brown);
  background-color: hsl(28 23% 41%);
  border-color: oklch(0.534 0.047 61.8);
}

Tailwind CSS v4

@theme {
  --color-pastel-brown: #816751;
  --color-pastel-brown-50: #fff3e8;
  --color-pastel-brown-100: #f4e5d8;
  --color-pastel-brown-200: #e3d1c0;
  --color-pastel-brown-300: #c9b39f;
  --color-pastel-brown-400: #b39983;
  --color-pastel-brown-500: #9d8067;
  --color-pastel-brown-600: #856c57;
  --color-pastel-brown-700: #6b5645;
  --color-pastel-brown-800: #4f3f32;
  --color-pastel-brown-900: #372b22;
  --color-pastel-brown-950: #221811;
}

SCSS

$pastel-brown: #816751;
$pastel-brown-rgb: 129, 103, 81;
$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);
}