#003A67

CSS

:root {
  --tardis-blue: #003a67;
  --tardis-blue-rgb: 0 58 103;
  --tardis-blue-oklch: oklch(0.342 0.095 249.3);
}

.element {
  color: var(--tardis-blue);
  background-color: hsl(206 100% 20%);
  border-color: oklch(0.342 0.095 249.3);
}

Tailwind CSS v4

@theme {
  --color-tardis-blue: #003a67;
  --color-tardis-blue-50: #e2f8ff;
  --color-tardis-blue-100: #d1ebff;
  --color-tardis-blue-200: #b7d8fc;
  --color-tardis-blue-300: #94bbe7;
  --color-tardis-blue-400: #72a3d5;
  --color-tardis-blue-500: #518bc3;
  --color-tardis-blue-600: #4575a4;
  --color-tardis-blue-700: #375e84;
  --color-tardis-blue-800: #254562;
  --color-tardis-blue-900: #193044;
  --color-tardis-blue-950: #091c2c;
}

SCSS

$tardis-blue: #003a67;
$tardis-blue-rgb: 0, 58, 103;
$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);
}