#003C6B

CSS

:root {
  --tardis-blue: #003c6b;
  --tardis-blue-rgb: 0 60 107;
  --tardis-blue-oklch: oklch(0.35 0.098 249.7);
}

.element {
  color: var(--tardis-blue);
  background-color: hsl(206 100% 21%);
  border-color: oklch(0.35 0.098 249.7);
}

Tailwind CSS v4

@theme {
  --color-tardis-blue: #003c6b;
  --color-tardis-blue-50: #e1f8ff;
  --color-tardis-blue-100: #d1ebff;
  --color-tardis-blue-200: #b6d8fe;
  --color-tardis-blue-300: #93bbe9;
  --color-tardis-blue-400: #70a3d6;
  --color-tardis-blue-500: #4f8ac5;
  --color-tardis-blue-600: #4475a6;
  --color-tardis-blue-700: #365e85;
  --color-tardis-blue-800: #244563;
  --color-tardis-blue-900: #183045;
  --color-tardis-blue-950: #091c2d;
}

SCSS

$tardis-blue: #003c6b;
$tardis-blue-rgb: 0, 60, 107;
$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);
}