#5D0000

CSS

:root {
  --spikey-red: #5d0000;
  --spikey-red-rgb: 93 0 0;
  --spikey-red-oklch: oklch(0.3 0.123 29.2);
}

.element {
  color: var(--spikey-red);
  background-color: hsl(0 100% 18%);
  border-color: oklch(0.3 0.123 29.2);
}

Tailwind CSS v4

@theme {
  --color-spikey-red: #5d0000;
  --color-spikey-red-50: #ffe9e0;
  --color-spikey-red-100: #ffdacf;
  --color-spikey-red-200: #ffc1b4;
  --color-spikey-red-300: #f0a091;
  --color-spikey-red-400: #de8173;
  --color-spikey-red-500: #cb6255;
  --color-spikey-red-600: #ab5448;
  --color-spikey-red-700: #8a4339;
  --color-spikey-red-800: #66302a;
  --color-spikey-red-900: #48201c;
  --color-spikey-red-950: #2f0f0d;
}

SCSS

$spikey-red: #5d0000;
$spikey-red-rgb: 93, 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);
}