#673841

CSS

:root {
  --red-rumour: #673841;
  --red-rumour-rgb: 103 56 65;
  --red-rumour-oklch: oklch(0.402 0.067 8.3);
}

.element {
  color: var(--red-rumour);
  background-color: hsl(349 30% 31%);
  border-color: oklch(0.402 0.067 8.3);
}

Tailwind CSS v4

@theme {
  --color-red-rumour: #673841;
  --color-red-rumour-50: #ffeef1;
  --color-red-rumour-100: #fddfe2;
  --color-red-rumour-200: #efc9cd;
  --color-red-rumour-300: #d7aaaf;
  --color-red-rumour-400: #c28e97;
  --color-red-rumour-500: #ad737d;
  --color-red-rumour-600: #93626a;
  --color-red-rumour-700: #764e55;
  --color-red-rumour-800: #57393f;
  --color-red-rumour-900: #3d272b;
  --color-red-rumour-950: #261518;
}

SCSS

$red-rumour: #673841;
$red-rumour-rgb: 103, 56, 65;
$red-rumour-light: mix(#fff, $red-rumour, 20%);
$red-rumour-dark: mix(#000, $red-rumour, 20%);

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