#050C51

CSS

:root {
  --interstellar-blue: #050c51;
  --interstellar-blue-rgb: 5 12 81;
  --interstellar-blue-oklch: oklch(0.218 0.122 267.1);
}

.element {
  color: var(--interstellar-blue);
  background-color: hsl(234 88% 17%);
  border-color: oklch(0.218 0.122 267.1);
}

Tailwind CSS v4

@theme {
  --color-interstellar-blue: #050c51;
  --color-interstellar-blue-50: #e7f5ff;
  --color-interstellar-blue-100: #d7e7ff;
  --color-interstellar-blue-200: #bfd3ff;
  --color-interstellar-blue-300: #9eb5f6;
  --color-interstellar-blue-400: #7e9ce7;
  --color-interstellar-blue-500: #6282d6;
  --color-interstellar-blue-600: #536eb5;
  --color-interstellar-blue-700: #425891;
  --color-interstellar-blue-800: #2e416c;
  --color-interstellar-blue-900: #1f2d4c;
  --color-interstellar-blue-950: #0f1932;
}

SCSS

$interstellar-blue: #050c51;
$interstellar-blue-rgb: 5, 12, 81;
$interstellar-blue-light: mix(#fff, $interstellar-blue, 20%);
$interstellar-blue-dark: mix(#000, $interstellar-blue, 20%);

.element {
  color: $interstellar-blue;
  box-shadow: 0 0 0 2px rgba($interstellar-blue, 0.35);
}