#40728F

CSS

:root {
  --harbour-blue: #40728f;
  --harbour-blue-rgb: 64 114 143;
  --harbour-blue-oklch: oklch(0.529 0.071 235.7);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(202 38% 41%);
  border-color: oklch(0.529 0.071 235.7);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #40728f;
  --color-harbour-blue-50: #e3f9ff;
  --color-harbour-blue-100: #d3ecfd;
  --color-harbour-blue-200: #b9d9ef;
  --color-harbour-blue-300: #96bdd8;
  --color-harbour-blue-400: #75a6c3;
  --color-harbour-blue-500: #558eaf;
  --color-harbour-blue-600: #497894;
  --color-harbour-blue-700: #3a6076;
  --color-harbour-blue-800: #284757;
  --color-harbour-blue-900: #1b313d;
  --color-harbour-blue-950: #0b1d26;
}

SCSS

$harbour-blue: #40728f;
$harbour-blue-rgb: 64, 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);
}