#45718D

CSS

:root {
  --harbour-blue: #45718d;
  --harbour-blue-rgb: 69 113 141;
  --harbour-blue-oklch: oklch(0.528 0.066 237.7);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(203 34% 41%);
  border-color: oklch(0.528 0.066 237.7);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #45718d;
  --color-harbour-blue-50: #e5f8ff;
  --color-harbour-blue-100: #d5ebfc;
  --color-harbour-blue-200: #bcd9ee;
  --color-harbour-blue-300: #99bdd6;
  --color-harbour-blue-400: #7aa5c1;
  --color-harbour-blue-500: #5b8dad;
  --color-harbour-blue-600: #4e7792;
  --color-harbour-blue-700: #3e5f75;
  --color-harbour-blue-800: #2b4656;
  --color-harbour-blue-900: #1d313c;
  --color-harbour-blue-950: #0d1d26;
}

SCSS

$harbour-blue: #45718d;
$harbour-blue-rgb: 69, 113, 141;
$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);
}