#3C728F

CSS

:root {
  --harbour-blue: #3c728f;
  --harbour-blue-rgb: 60 114 143;
  --harbour-blue-oklch: oklch(0.527 0.073 234);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(201 41% 40%);
  border-color: oklch(0.527 0.073 234);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #3c728f;
  --color-harbour-blue-50: #e2f9ff;
  --color-harbour-blue-100: #d2ecfe;
  --color-harbour-blue-200: #b7daf0;
  --color-harbour-blue-300: #94bed8;
  --color-harbour-blue-400: #72a6c3;
  --color-harbour-blue-500: #528eaf;
  --color-harbour-blue-600: #467894;
  --color-harbour-blue-700: #386077;
  --color-harbour-blue-800: #264757;
  --color-harbour-blue-900: #1a313d;
  --color-harbour-blue-950: #0a1d27;
}

SCSS

$harbour-blue: #3c728f;
$harbour-blue-rgb: 60, 114, 143;
$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);
}