#03151D

CSS

:root {
  --black-stallion: #03151d;
  --black-stallion-rgb: 3 21 29;
  --black-stallion-oklch: oklch(0.184 0.03 228);
}

.element {
  color: var(--black-stallion);
  background-color: hsl(198 81% 6%);
  border-color: oklch(0.184 0.03 228);
}

Tailwind CSS v4

@theme {
  --color-black-stallion: #03151d;
  --color-black-stallion-50: #edf7fc;
  --color-black-stallion-100: #deeaf0;
  --color-black-stallion-200: #c8d7df;
  --color-black-stallion-300: #a8bbc4;
  --color-black-stallion-400: #8da2ad;
  --color-black-stallion-500: #728b96;
  --color-black-stallion-600: #61757f;
  --color-black-stallion-700: #4d5e66;
  --color-black-stallion-800: #38454a;
  --color-black-stallion-900: #263034;
  --color-black-stallion-950: #141c1f;
}

SCSS

$black-stallion: #03151d;
$black-stallion-rgb: 3, 21, 29;
$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);
}