#00314A

CSS

:root {
  --sea-of-stars: #00314a;
  --sea-of-stars-rgb: 0 49 74;
  --sea-of-stars-oklch: oklch(0.297 0.066 238);
}

.element {
  color: var(--sea-of-stars);
  background-color: hsl(200 100% 15%);
  border-color: oklch(0.297 0.066 238);
}

Tailwind CSS v4

@theme {
  --color-sea-of-stars: #00314a;
  --color-sea-of-stars-50: #e5f8ff;
  --color-sea-of-stars-100: #d5ebfc;
  --color-sea-of-stars-200: #bcd9ee;
  --color-sea-of-stars-300: #99bdd6;
  --color-sea-of-stars-400: #7aa5c1;
  --color-sea-of-stars-500: #5b8dad;
  --color-sea-of-stars-600: #4e7792;
  --color-sea-of-stars-700: #3e5f75;
  --color-sea-of-stars-800: #2b4656;
  --color-sea-of-stars-900: #1d303c;
  --color-sea-of-stars-950: #0d1d26;
}

SCSS

$sea-of-stars: #00314a;
$sea-of-stars-rgb: 0, 49, 74;
$sea-of-stars-light: mix(#fff, $sea-of-stars, 20%);
$sea-of-stars-dark: mix(#000, $sea-of-stars, 20%);

.element {
  color: $sea-of-stars;
  box-shadow: 0 0 0 2px rgba($sea-of-stars, 0.35);
}