#003B80

CSS

:root {
  --tardis-blue: #003b80;
  --tardis-blue-rgb: 0 59 128;
  --tardis-blue-oklch: oklch(0.364 0.129 256.9);
}

.element {
  color: var(--tardis-blue);
  background-color: hsl(212 100% 25%);
  border-color: oklch(0.364 0.129 256.9);
}

Tailwind CSS v4

@theme {
  --color-tardis-blue: #003b80;
  --color-tardis-blue-50: #dff7ff;
  --color-tardis-blue-100: #ceeaff;
  --color-tardis-blue-200: #b3d6ff;
  --color-tardis-blue-300: #8fb9f9;
  --color-tardis-blue-400: #6ba0ea;
  --color-tardis-blue-500: #4a86da;
  --color-tardis-blue-600: #3f72b8;
  --color-tardis-blue-700: #325b94;
  --color-tardis-blue-800: #21436e;
  --color-tardis-blue-900: #152e4d;
  --color-tardis-blue-950: #071b33;
}

SCSS

$tardis-blue: #003b80;
$tardis-blue-rgb: 0, 59, 128;
$tardis-blue-light: mix(#fff, $tardis-blue, 20%);
$tardis-blue-dark: mix(#000, $tardis-blue, 20%);

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