#3B7294

CSS

:root {
  --harbour-blue: #3b7294;
  --harbour-blue-rgb: 59 114 148;
  --harbour-blue-oklch: oklch(0.529 0.079 237.9);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(203 43% 41%);
  border-color: oklch(0.529 0.079 237.9);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #3b7294;
  --color-harbour-blue-50: #e2f9ff;
  --color-harbour-blue-100: #d1ecff;
  --color-harbour-blue-200: #b6daf3;
  --color-harbour-blue-300: #93bedc;
  --color-harbour-blue-400: #71a6c8;
  --color-harbour-blue-500: #508eb5;
  --color-harbour-blue-600: #447898;
  --color-harbour-blue-700: #36607a;
  --color-harbour-blue-800: #25475a;
  --color-harbour-blue-900: #19313f;
  --color-harbour-blue-950: #091d28;
}

SCSS

$harbour-blue: #3b7294;
$harbour-blue-rgb: 59, 114, 148;
$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);
}