#DA002F

CSS

:root {
  --rare-red: #da002f;
  --rare-red-rgb: 218 0 47;
  --rare-red-oklch: oklch(0.561 0.226 22.5);
}

.element {
  color: var(--rare-red);
  background-color: hsl(347 100% 43%);
  border-color: oklch(0.561 0.226 22.5);
}

Tailwind CSS v4

@theme {
  --color-rare-red: #da002f;
  --color-rare-red-50: #ffdcd5;
  --color-rare-red-100: #ffcac2;
  --color-rare-red-200: #ffaca4;
  --color-rare-red-300: #ff827c;
  --color-rare-red-400: #ff565d;
  --color-rare-red-500: #f90538;
  --color-rare-red-600: #d21230;
  --color-rare-red-700: #a91126;
  --color-rare-red-800: #7e081e;
  --color-rare-red-900: #5a0614;
  --color-rare-red-950: #3c0006;
}

SCSS

$rare-red: #da002f;
$rare-red-rgb: 218, 0, 47;
$rare-red-light: mix(#fff, $rare-red, 20%);
$rare-red-dark: mix(#000, $rare-red, 20%);

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