#C60001

CSS

:root {
  --threatening-red: #c60001;
  --threatening-red-rgb: 198 0 1;
  --threatening-red-oklch: oklch(0.519 0.213 29.1);
}

.element {
  color: var(--threatening-red);
  background-color: hsl(360 100% 39%);
  border-color: oklch(0.519 0.213 29.1);
}

Tailwind CSS v4

@theme {
  --color-threatening-red: #c60001;
  --color-threatening-red-50: #ffdfd0;
  --color-threatening-red-100: #ffcebc;
  --color-threatening-red-200: #ffb19c;
  --color-threatening-red-300: #ff8871;
  --color-threatening-red-400: #ff5f4e;
  --color-threatening-red-500: #f3291e;
  --color-threatening-red-600: #cd271d;
  --color-threatening-red-700: #a52017;
  --color-threatening-red-800: #7c1413;
  --color-threatening-red-900: #580d0c;
  --color-threatening-red-950: #3b0001;
}

SCSS

$threatening-red: #c60001;
$threatening-red-rgb: 198, 0, 1;
$threatening-red-light: mix(#fff, $threatening-red, 20%);
$threatening-red-dark: mix(#000, $threatening-red, 20%);

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