#3E728D

CSS

:root {
  --harbour-blue: #3e728d;
  --harbour-blue-rgb: 62 114 141;
  --harbour-blue-oklch: oklch(0.527 0.07 232.9);
}

.element {
  color: var(--harbour-blue);
  background-color: hsl(201 39% 40%);
  border-color: oklch(0.527 0.07 232.9);
}

Tailwind CSS v4

@theme {
  --color-harbour-blue: #3e728d;
  --color-harbour-blue-50: #e3f9ff;
  --color-harbour-blue-100: #d2ecfc;
  --color-harbour-blue-200: #b8daee;
  --color-harbour-blue-300: #95bed6;
  --color-harbour-blue-400: #74a6c1;
  --color-harbour-blue-500: #548ead;
  --color-harbour-blue-600: #487892;
  --color-harbour-blue-700: #396075;
  --color-harbour-blue-800: #274756;
  --color-harbour-blue-900: #1a313c;
  --color-harbour-blue-950: #0b1d26;
}

SCSS

$harbour-blue: #3e728d;
$harbour-blue-rgb: 62, 114, 141;
$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);
}