#183654

CSS

:root {
  --beyond-the-stars: #183654;
  --beyond-the-stars-rgb: 24 54 84;
  --beyond-the-stars-oklch: oklch(0.326 0.065 250.4);
}

.element {
  color: var(--beyond-the-stars);
  background-color: hsl(210 56% 21%);
  border-color: oklch(0.326 0.065 250.4);
}

Tailwind CSS v4

@theme {
  --color-beyond-the-stars: #183654;
  --color-beyond-the-stars-50: #e8f7ff;
  --color-beyond-the-stars-100: #d9eafe;
  --color-beyond-the-stars-200: #c1d7f0;
  --color-beyond-the-stars-300: #a0bad8;
  --color-beyond-the-stars-400: #82a2c4;
  --color-beyond-the-stars-500: #658ab0;
  --color-beyond-the-stars-600: #567495;
  --color-beyond-the-stars-700: #455d77;
  --color-beyond-the-stars-800: #304458;
  --color-beyond-the-stars-900: #212f3d;
  --color-beyond-the-stars-950: #101c27;
}

SCSS

$beyond-the-stars: #183654;
$beyond-the-stars-rgb: 24, 54, 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);
}