#9B0000

CSS

:root {
  --cacodemon-red: #9b0000;
  --cacodemon-red-rgb: 155 0 0;
  --cacodemon-red-oklch: oklch(0.433 0.178 29.2);
}

.element {
  color: var(--cacodemon-red);
  background-color: hsl(0 100% 30%);
  border-color: oklch(0.433 0.178 29.2);
}

Tailwind CSS v4

@theme {
  --color-cacodemon-red: #9b0000;
  --color-cacodemon-red-50: #ffe3d6;
  --color-cacodemon-red-100: #ffd3c4;
  --color-cacodemon-red-200: #ffb8a5;
  --color-cacodemon-red-300: #ff927e;
  --color-cacodemon-red-400: #f56f5e;
  --color-cacodemon-red-500: #e44739;
  --color-cacodemon-red-600: #c03e31;
  --color-cacodemon-red-700: #9b3127;
  --color-cacodemon-red-800: #74221d;
  --color-cacodemon-red-900: #521713;
  --color-cacodemon-red-950: #360605;
}

SCSS

$cacodemon-red: #9b0000;
$cacodemon-red-rgb: 155, 0, 0;
$cacodemon-red-light: mix(#fff, $cacodemon-red, 20%);
$cacodemon-red-dark: mix(#000, $cacodemon-red, 20%);

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