#515151

CSS

:root {
  --stone-cold: #515151;
  --stone-cold-rgb: 81 81 81;
  --stone-cold-oklch: oklch(0.435 0 0);
}

.element {
  color: var(--stone-cold);
  background-color: hsl(0 0% 32%);
  border-color: oklch(0.435 0 0);
}

Tailwind CSS v4

@theme {
  --color-stone-cold: #515151;
  --color-stone-cold-50: #f5f5f5;
  --color-stone-cold-100: #e8e8e8;
  --color-stone-cold-200: #d4d4d4;
  --color-stone-cold-300: #b7b7b7;
  --color-stone-cold-400: #9e9e9e;
  --color-stone-cold-500: #868686;
  --color-stone-cold-600: #717171;
  --color-stone-cold-700: #5b5b5b;
  --color-stone-cold-800: #424242;
  --color-stone-cold-900: #2e2e2e;
  --color-stone-cold-950: #1b1b1b;
}

SCSS

$stone-cold: #515151;
$stone-cold-rgb: 81, 81, 81;
$stone-cold-light: mix(#fff, $stone-cold, 20%);
$stone-cold-dark: mix(#000, $stone-cold, 20%);

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