#0F1F2B

CSS

:root {
  --the-count-s-black: #0f1f2b;
  --the-count-s-black-rgb: 15 31 43;
  --the-count-s-black-oklch: oklch(0.231 0.032 242.3);
}

.element {
  color: var(--the-count-s-black);
  background-color: hsl(206 48% 11%);
  border-color: oklch(0.231 0.032 242.3);
}

Tailwind CSS v4

@theme {
  --color-the-count-s-black: #0f1f2b;
  --color-the-count-s-black-50: #eef6fe;
  --color-the-count-s-black-100: #dfe9f2;
  --color-the-count-s-black-200: #c9d6e1;
  --color-the-count-s-black-300: #aabac7;
  --color-the-count-s-black-400: #8fa1b0;
  --color-the-count-s-black-500: #74899a;
  --color-the-count-s-black-600: #637482;
  --color-the-count-s-black-700: #4f5d68;
  --color-the-count-s-black-800: #39444d;
  --color-the-count-s-black-900: #272f35;
  --color-the-count-s-black-950: #151c20;
}

SCSS

$the-count-s-black: #0f1f2b;
$the-count-s-black-rgb: 15, 31, 43;
$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);
}