#3A7290

CSS

:root {
  --harbour-blue: #3a7290;
  --harbour-blue-rgb: 58 114 144;
  --harbour-blue-oklch: oklch(0.527 0.076 234.1);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(201 43% 40%);
  border-color: oklch(0.527 0.076 234.1);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #3a7290;
  --color-harbour-blue-50: #e2f9ff;
  --color-harbour-blue-100: #d1ecfe;
  --color-harbour-blue-200: #b6daf1;
  --color-harbour-blue-300: #93bed9;
  --color-harbour-blue-400: #71a6c5;
  --color-harbour-blue-500: #508eb1;
  --color-harbour-blue-600: #447995;
  --color-harbour-blue-700: #366178;
  --color-harbour-blue-800: #254758;
  --color-harbour-blue-900: #19313e;
  --color-harbour-blue-950: #091d27;
}

SCSS

$harbour-blue: #3a7290;
$harbour-blue-rgb: 58, 114, 144;
$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);
}