#377291

CSS

:root {
  --harbour-blue: #377291;
  --harbour-blue-rgb: 55 114 145;
  --harbour-blue-oklch: oklch(0.526 0.078 233.9);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(201 45% 39%);
  border-color: oklch(0.526 0.078 233.9);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #377291;
  --color-harbour-blue-50: #e1f9ff;
  --color-harbour-blue-100: #d0edff;
  --color-harbour-blue-200: #b5daf2;
  --color-harbour-blue-300: #91bedb;
  --color-harbour-blue-400: #6fa7c6;
  --color-harbour-blue-500: #4d8fb2;
  --color-harbour-blue-600: #427997;
  --color-harbour-blue-700: #346179;
  --color-harbour-blue-800: #244759;
  --color-harbour-blue-900: #18313e;
  --color-harbour-blue-950: #081d27;
}

SCSS

$harbour-blue: #377291;
$harbour-blue-rgb: 55, 114, 145;
$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);
}