#45718E

CSS

:root {
  --harbour-blue: #45718e;
  --harbour-blue-rgb: 69 113 142;
  --harbour-blue-oklch: oklch(0.529 0.067 238.7);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(204 35% 41%);
  border-color: oklch(0.529 0.067 238.7);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #45718e;
  --color-harbour-blue-50: #e5f8ff;
  --color-harbour-blue-100: #d5ebfd;
  --color-harbour-blue-200: #bcd9ef;
  --color-harbour-blue-300: #99bdd7;
  --color-harbour-blue-400: #7aa5c2;
  --color-harbour-blue-500: #5b8dae;
  --color-harbour-blue-600: #4d7793;
  --color-harbour-blue-700: #3e5f76;
  --color-harbour-blue-800: #2b4657;
  --color-harbour-blue-900: #1d303d;
  --color-harbour-blue-950: #0d1d26;
}

SCSS

$harbour-blue: #45718e;
$harbour-blue-rgb: 69, 113, 142;
$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);
}