#AD3C00

CSS

:root {
  --rust: #ad3c00;
  --rust-rgb: 173 60 0;
  --rust-oklch: oklch(0.512 0.158 40.7);
}

.element {
  color: var(--rust);
  background-color: hsl(21 100% 34%);
  border-color: oklch(0.512 0.158 40.7);
}

Tailwind CSS v4

@theme {
  --color-rust: #ad3c00;
  --color-rust-50: #ffe7d2;
  --color-rust-100: #ffd7be;
  --color-rust-200: #ffbe9e;
  --color-rust-300: #fb9b74;
  --color-rust-400: #eb7a50;
  --color-rust-500: #d95821;
  --color-rust-600: #b74b1f;
  --color-rust-700: #933c19;
  --color-rust-800: #6e2a13;
  --color-rust-900: #4e1c0c;
  --color-rust-950: #330c01;
}

SCSS

$rust: #ad3c00;
$rust-rgb: 173, 60, 0;
$rust-light: mix(#fff, $rust, 20%);
$rust-dark: mix(#000, $rust, 20%);

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