#8B1500

CSS

:root {
  --brick-red: #8b1500;
  --brick-red-rgb: 139 21 0;
  --brick-red-oklch: oklch(0.41 0.155 32.2);
}

.element {
  color: var(--brick-red);
  background-color: hsl(9 100% 27%);
  border-color: oklch(0.41 0.155 32.2);
}

Tailwind CSS v4

@theme {
  --color-brick-red: #8b1500;
  --color-brick-red-50: #ffe6d8;
  --color-brick-red-100: #ffd6c6;
  --color-brick-red-200: #ffbda8;
  --color-brick-red-300: #fc9982;
  --color-brick-red-400: #eb7862;
  --color-brick-red-500: #d9563e;
  --color-brick-red-600: #b74936;
  --color-brick-red-700: #933b2b;
  --color-brick-red-800: #6e2920;
  --color-brick-red-900: #4e1c15;
  --color-brick-red-950: #330b06;
}

SCSS

$brick-red: #8b1500;
$brick-red-rgb: 139, 21, 0;
$brick-red-light: mix(#fff, $brick-red, 20%);
$brick-red-dark: mix(#000, $brick-red, 20%);

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