#3C7293

CSS

:root {
  --harbour-blue: #3c7293;
  --harbour-blue-rgb: 60 114 147;
  --harbour-blue-oklch: oklch(0.529 0.078 237.5);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(203 42% 41%);
  border-color: oklch(0.529 0.078 237.5);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #3c7293;
  --color-harbour-blue-50: #e2f9ff;
  --color-harbour-blue-100: #d1ecff;
  --color-harbour-blue-200: #b7daf2;
  --color-harbour-blue-300: #93bddb;
  --color-harbour-blue-400: #72a6c7;
  --color-harbour-blue-500: #518eb3;
  --color-harbour-blue-600: #457898;
  --color-harbour-blue-700: #37607a;
  --color-harbour-blue-800: #26475a;
  --color-harbour-blue-900: #19313f;
  --color-harbour-blue-950: #0a1d28;
}

SCSS

$harbour-blue: #3c7293;
$harbour-blue-rgb: 60, 114, 147;
$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);
}