#48718A

CSS

:root {
  --harbour-blue: #48718a;
  --harbour-blue-rgb: 72 113 138;
  --harbour-blue-oklch: oklch(0.529 0.06 236.3);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(203 31% 41%);
  border-color: oklch(0.529 0.06 236.3);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #48718a;
  --color-harbour-blue-50: #e6f8ff;
  --color-harbour-blue-100: #d6ebfa;
  --color-harbour-blue-200: #bdd9ec;
  --color-harbour-blue-300: #9bbcd3;
  --color-harbour-blue-400: #7ca5be;
  --color-harbour-blue-500: #5e8da9;
  --color-harbour-blue-600: #50778f;
  --color-harbour-blue-700: #405f73;
  --color-harbour-blue-800: #2d4654;
  --color-harbour-blue-900: #1e303b;
  --color-harbour-blue-950: #0e1d25;
}

SCSS

$harbour-blue: #48718a;
$harbour-blue-rgb: 72, 113, 138;
$harbour-blue-light: mix(#fff, $harbour-blue, 20%);
$harbour-blue-dark: mix(#000, $harbour-blue, 20%);

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