#0C1827

CSS

:root {
  --the-count-s-black: #0c1827;
  --the-count-s-black-rgb: 12 24 39;
  --the-count-s-black-oklch: oklch(0.206 0.035 254.6);
}

.element {
  color: var(--the-count-s-black);
  background-color: hsl(213 53% 10%);
  border-color: oklch(0.206 0.035 254.6);
}

Tailwind CSS v4

@theme {
  --color-the-count-s-black: #0c1827;
  --color-the-count-s-black-50: #eff6ff;
  --color-the-count-s-black-100: #e1e9f4;
  --color-the-count-s-black-200: #cbd5e3;
  --color-the-count-s-black-300: #acb8c9;
  --color-the-count-s-black-400: #91a0b3;
  --color-the-count-s-black-500: #77889d;
  --color-the-count-s-black-600: #657385;
  --color-the-count-s-black-700: #505c6b;
  --color-the-count-s-black-800: #3a434e;
  --color-the-count-s-black-900: #282e36;
  --color-the-count-s-black-950: #161b21;
}

SCSS

$the-count-s-black: #0c1827;
$the-count-s-black-rgb: 12, 24, 39;
$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);
}