#003A7B

CSS

:root {
  --tardis-blue: #003a7b;
  --tardis-blue-rgb: 0 58 123;
  --tardis-blue-oklch: oklch(0.358 0.123 256.2);
}

.element {
  color: var(--tardis-blue);
  background-color: hsl(212 100% 24%);
  border-color: oklch(0.358 0.123 256.2);
}

Tailwind CSS v4

@theme {
  --color-tardis-blue: #003a7b;
  --color-tardis-blue-50: #e0f7ff;
  --color-tardis-blue-100: #cfeaff;
  --color-tardis-blue-200: #b4d6ff;
  --color-tardis-blue-300: #90b9f6;
  --color-tardis-blue-400: #6da0e6;
  --color-tardis-blue-500: #4c87d6;
  --color-tardis-blue-600: #4172b5;
  --color-tardis-blue-700: #335c91;
  --color-tardis-blue-800: #22436c;
  --color-tardis-blue-900: #162f4c;
  --color-tardis-blue-950: #071b32;
}

SCSS

$tardis-blue: #003a7b;
$tardis-blue-rgb: 0, 58, 123;
$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);
}