#003054

CSS

:root {
  --beyond-the-stars: #003054;
  --beyond-the-stars-rgb: 0 48 84;
  --beyond-the-stars-oklch: oklch(0.301 0.08 247.6);
}

.element {
  color: var(--beyond-the-stars);
  background-color: hsl(206 100% 16%);
  border-color: oklch(0.301 0.08 247.6);
}

Tailwind CSS v4

@theme {
  --color-beyond-the-stars: #003054;
  --color-beyond-the-stars-50: #e4f8ff;
  --color-beyond-the-stars-100: #d4ebff;
  --color-beyond-the-stars-200: #bbd8f6;
  --color-beyond-the-stars-300: #98bbe0;
  --color-beyond-the-stars-400: #78a3cc;
  --color-beyond-the-stars-500: #598bb9;
  --color-beyond-the-stars-600: #4c769c;
  --color-beyond-the-stars-700: #3c5e7d;
  --color-beyond-the-stars-800: #2a455d;
  --color-beyond-the-stars-900: #1c3041;
  --color-beyond-the-stars-950: #0c1c29;
}

SCSS

$beyond-the-stars: #003054;
$beyond-the-stars-rgb: 0, 48, 84;
$beyond-the-stars-light: mix(#fff, $beyond-the-stars, 20%);
$beyond-the-stars-dark: mix(#000, $beyond-the-stars, 20%);

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