#A90105

CSS

:root {
  --velvet-volcano: #a90105;
  --velvet-volcano-rgb: 169 1 5;
  --velvet-volcano-oklch: oklch(0.462 0.189 28.6);
}

.element {
  color: var(--velvet-volcano);
  background-color: hsl(359 99% 33%);
  border-color: oklch(0.462 0.189 28.6);
}

Tailwind CSS v4

@theme {
  --color-velvet-volcano: #a90105;
  --color-velvet-volcano-50: #ffe2d5;
  --color-velvet-volcano-100: #ffd1c2;
  --color-velvet-volcano-200: #ffb5a3;
  --color-velvet-volcano-300: #ff8f7b;
  --color-velvet-volcano-400: #fa6a5b;
  --color-velvet-volcano-500: #e93f34;
  --color-velvet-volcano-600: #c4382d;
  --color-velvet-volcano-700: #9e2d24;
  --color-velvet-volcano-800: #761e1b;
  --color-velvet-volcano-900: #541412;
  --color-velvet-volcano-950: #380405;
}

SCSS

$velvet-volcano: #a90105;
$velvet-volcano-rgb: 169, 1, 5;
$velvet-volcano-light: mix(#fff, $velvet-volcano, 20%);
$velvet-volcano-dark: mix(#000, $velvet-volcano, 20%);

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