#003757

CSS

:root {
  --sea-of-stars: #003757;
  --sea-of-stars-rgb: 0 55 87;
  --sea-of-stars-oklch: oklch(0.323 0.077 242.1);
}

.element {
  color: var(--sea-of-stars);
  background-color: hsl(202 100% 17%);
  border-color: oklch(0.323 0.077 242.1);
}

Tailwind CSS v4

@theme {
  --color-sea-of-stars: #003757;
  --color-sea-of-stars-50: #e3f8ff;
  --color-sea-of-stars-100: #d3ebff;
  --color-sea-of-stars-200: #b9d9f3;
  --color-sea-of-stars-300: #96bcdc;
  --color-sea-of-stars-400: #76a4c8;
  --color-sea-of-stars-500: #568cb5;
  --color-sea-of-stars-600: #497799;
  --color-sea-of-stars-700: #3a5f7b;
  --color-sea-of-stars-800: #28465a;
  --color-sea-of-stars-900: #1b303f;
  --color-sea-of-stars-950: #0b1d28;
}

SCSS

$sea-of-stars: #003757;
$sea-of-stars-rgb: 0, 55, 87;
$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);
}