#001721

CSS

:root {
  --black-stallion: #001721;
  --black-stallion-rgb: 0 23 33;
  --black-stallion-oklch: oklch(0.191 0.037 227.9);
}

.element {
  color: var(--black-stallion);
  background-color: hsl(198 100% 6%);
  border-color: oklch(0.191 0.037 227.9);
}

Tailwind CSS v4

@theme {
  --color-black-stallion: #001721;
  --color-black-stallion-50: #ebf7fe;
  --color-black-stallion-100: #dcebf2;
  --color-black-stallion-200: #c5d8e1;
  --color-black-stallion-300: #a5bbc7;
  --color-black-stallion-400: #88a3b0;
  --color-black-stallion-500: #6d8c9a;
  --color-black-stallion-600: #5c7682;
  --color-black-stallion-700: #4a5e68;
  --color-black-stallion-800: #35454c;
  --color-black-stallion-900: #243035;
  --color-black-stallion-950: #131c20;
}

SCSS

$black-stallion: #001721;
$black-stallion-rgb: 0, 23, 33;
$black-stallion-light: mix(#fff, $black-stallion, 20%);
$black-stallion-dark: mix(#000, $black-stallion, 20%);

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