#030C53

CSS

:root {
  --interstellar-blue: #030c53;
  --interstellar-blue-rgb: 3 12 83;
  --interstellar-blue-oklch: oklch(0.22 0.125 265.8);
}

.element {
  color: var(--interstellar-blue);
  background-color: hsl(233 93% 17%);
  border-color: oklch(0.22 0.125 265.8);
}

Tailwind CSS v4

@theme {
  --color-interstellar-blue: #030c53;
  --color-interstellar-blue-50: #e6f5ff;
  --color-interstellar-blue-100: #d6e7ff;
  --color-interstellar-blue-200: #bdd3ff;
  --color-interstellar-blue-300: #9cb5f8;
  --color-interstellar-blue-400: #7b9ce9;
  --color-interstellar-blue-500: #5f82d9;
  --color-interstellar-blue-600: #506eb7;
  --color-interstellar-blue-700: #405893;
  --color-interstellar-blue-800: #2c416d;
  --color-interstellar-blue-900: #1d2d4d;
  --color-interstellar-blue-950: #0e1933;
}

SCSS

$interstellar-blue: #030c53;
$interstellar-blue-rgb: 3, 12, 83;
$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);
}