#003B65

CSS

:root {
  --tardis-blue: #003b65;
  --tardis-blue-rgb: 0 59 101;
  --tardis-blue-oklch: oklch(0.343 0.091 247.4);
}

.element {
  color: var(--tardis-blue);
  background-color: hsl(205 100% 20%);
  border-color: oklch(0.343 0.091 247.4);
}

Tailwind CSS v4

@theme {
  --color-tardis-blue: #003b65;
  --color-tardis-blue-50: #e2f8ff;
  --color-tardis-blue-100: #d1ebff;
  --color-tardis-blue-200: #b7d8fa;
  --color-tardis-blue-300: #94bce5;
  --color-tardis-blue-400: #72a4d2;
  --color-tardis-blue-500: #518bbf;
  --color-tardis-blue-600: #4676a2;
  --color-tardis-blue-700: #375e82;
  --color-tardis-blue-800: #264560;
  --color-tardis-blue-900: #193043;
  --color-tardis-blue-950: #0a1c2b;
}

SCSS

$tardis-blue: #003b65;
$tardis-blue-rgb: 0, 59, 101;
$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);
}