#003750

CSS

:root {
  --sea-of-stars: #003750;
  --sea-of-stars-rgb: 0 55 80;
  --sea-of-stars-oklch: oklch(0.318 0.068 235.6);
}

.element {
  color: var(--sea-of-stars);
  background-color: hsl(199 100% 16%);
  border-color: oklch(0.318 0.068 235.6);
}

Tailwind CSS v4

@theme {
  --color-sea-of-stars: #003750;
  --color-sea-of-stars-50: #e4f9ff;
  --color-sea-of-stars-100: #d4ecfc;
  --color-sea-of-stars-200: #bad9ee;
  --color-sea-of-stars-300: #97bdd7;
  --color-sea-of-stars-400: #77a5c1;
  --color-sea-of-stars-500: #578dad;
  --color-sea-of-stars-600: #4b7892;
  --color-sea-of-stars-700: #3b6075;
  --color-sea-of-stars-800: #294656;
  --color-sea-of-stars-900: #1c313c;
  --color-sea-of-stars-950: #0c1d26;
}

SCSS

$sea-of-stars: #003750;
$sea-of-stars-rgb: 0, 55, 80;
$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);
}