#0A1828

CSS

:root {
  --the-count-s-black: #0a1828;
  --the-count-s-black-rgb: 10 24 40;
  --the-count-s-black-oklch: oklch(0.206 0.038 252.9);
}

.element {
  color: var(--the-count-s-black);
  background-color: hsl(212 60% 10%);
  border-color: oklch(0.206 0.038 252.9);
}

Tailwind CSS v4

@theme {
  --color-the-count-s-black: #0a1828;
  --color-the-count-s-black-50: #eef6ff;
  --color-the-count-s-black-100: #e0e9f5;
  --color-the-count-s-black-200: #cad5e5;
  --color-the-count-s-black-300: #abb9cb;
  --color-the-count-s-black-400: #8fa0b5;
  --color-the-count-s-black-500: #75889f;
  --color-the-count-s-black-600: #637386;
  --color-the-count-s-black-700: #4f5c6c;
  --color-the-count-s-black-800: #39444f;
  --color-the-count-s-black-900: #272f37;
  --color-the-count-s-black-950: #151b22;
}

SCSS

$the-count-s-black: #0a1828;
$the-count-s-black-rgb: 10, 24, 40;
$the-count-s-black-light: mix(#fff, $the-count-s-black, 20%);
$the-count-s-black-dark: mix(#000, $the-count-s-black, 20%);

.element {
  color: $the-count-s-black;
  box-shadow: 0 0 0 2px rgba($the-count-s-black, 0.35);
}