#43718C

CSS

:root {
  --harbour-blue: #43718c;
  --harbour-blue-rgb: 67 113 140;
  --harbour-blue-oklch: oklch(0.527 0.066 235.7);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(202 35% 41%);
  border-color: oklch(0.527 0.066 235.7);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #43718c;
  --color-harbour-blue-50: #e4f8ff;
  --color-harbour-blue-100: #d4ecfc;
  --color-harbour-blue-200: #bbd9ee;
  --color-harbour-blue-300: #98bdd6;
  --color-harbour-blue-400: #78a5c0;
  --color-harbour-blue-500: #598dac;
  --color-harbour-blue-600: #4c7891;
  --color-harbour-blue-700: #3d6075;
  --color-harbour-blue-800: #2a4656;
  --color-harbour-blue-900: #1c313c;
  --color-harbour-blue-950: #0c1d26;
}

SCSS

$harbour-blue: #43718c;
$harbour-blue-rgb: 67, 113, 140;
$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);
}