#650000

CSS

:root {
  --spikey-red: #650000;
  --spikey-red-rgb: 101 0 0;
  --spikey-red-oklch: oklch(0.318 0.131 29.2);
}

.element {
  color: var(--spikey-red);
  background-color: hsl(0 100% 20%);
  border-color: oklch(0.318 0.131 29.2);
}

Tailwind CSS v4

@theme {
  --color-spikey-red: #650000;
  --color-spikey-red-50: #ffe8df;
  --color-spikey-red-100: #ffd9ce;
  --color-spikey-red-200: #ffc0b2;
  --color-spikey-red-300: #f39e8e;
  --color-spikey-red-400: #e17f71;
  --color-spikey-red-500: #ce5f51;
  --color-spikey-red-600: #ae5145;
  --color-spikey-red-700: #8c4137;
  --color-spikey-red-800: #682e29;
  --color-spikey-red-900: #491f1b;
  --color-spikey-red-950: #300e0c;
}

SCSS

$spikey-red: #650000;
$spikey-red-rgb: 101, 0, 0;
$spikey-red-light: mix(#fff, $spikey-red, 20%);
$spikey-red-dark: mix(#000, $spikey-red, 20%);

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