#D51C21

CSS

:root {
  --heroic-red: #d51c21;
  --heroic-red-rgb: 213 28 33;
  --heroic-red-oklch: oklch(0.558 0.215 27);
}

.element {
  color: var(--heroic-red);
  background-color: hsl(358 77% 47%);
  border-color: oklch(0.558 0.215 27);
}

Tailwind CSS v4

@theme {
  --color-heroic-red: #d51c21;
  --color-heroic-red-50: #ffdfd2;
  --color-heroic-red-100: #ffcdbf;
  --color-heroic-red-200: #ffb09f;
  --color-heroic-red-300: #ff8775;
  --color-heroic-red-400: #ff5e54;
  --color-heroic-red-500: #f42529;
  --color-heroic-red-600: #ce2425;
  --color-heroic-red-700: #a61d1d;
  --color-heroic-red-800: #7c1217;
  --color-heroic-red-900: #580c0f;
  --color-heroic-red-950: #3b0003;
}

SCSS

$heroic-red: #d51c21;
$heroic-red-rgb: 213, 28, 33;
$heroic-red-light: mix(#fff, $heroic-red, 20%);
$heroic-red-dark: mix(#000, $heroic-red, 20%);

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