#003B58

CSS

:root {
  --sea-of-stars: #003b58;
  --sea-of-stars-rgb: 0 59 88;
  --sea-of-stars-oklch: oklch(0.335 0.074 238.1);
}

.element {
  color: var(--sea-of-stars);
  background-color: hsl(200 100% 17%);
  border-color: oklch(0.335 0.074 238.1);
}

Tailwind CSS v4

@theme {
  --color-sea-of-stars: #003b58;
  --color-sea-of-stars-50: #e3f9ff;
  --color-sea-of-stars-100: #d3ecff;
  --color-sea-of-stars-200: #b9d9f1;
  --color-sea-of-stars-300: #95bdda;
  --color-sea-of-stars-400: #74a5c6;
  --color-sea-of-stars-500: #548db2;
  --color-sea-of-stars-600: #487896;
  --color-sea-of-stars-700: #396078;
  --color-sea-of-stars-800: #284659;
  --color-sea-of-stars-900: #1b313e;
  --color-sea-of-stars-950: #0b1d27;
}

SCSS

$sea-of-stars: #003b58;
$sea-of-stars-rgb: 0, 59, 88;
$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);
}