#66749B

CSS

:root {
  --misty-harbour: #66749b;
  --misty-harbour-rgb: 102 116 155;
  --misty-harbour-oklch: oklch(0.563 0.063 269.1);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(224 21% 50%);
  border-color: oklch(0.563 0.063 269.1);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #66749b;
  --color-misty-harbour-50: #eef5ff;
  --color-misty-harbour-100: #e0e7fe;
  --color-misty-harbour-200: #cad3f0;
  --color-misty-harbour-300: #abb6d9;
  --color-misty-harbour-400: #8f9dc5;
  --color-misty-harbour-500: #7585b1;
  --color-misty-harbour-600: #637095;
  --color-misty-harbour-700: #4f5a78;
  --color-misty-harbour-800: #394259;
  --color-misty-harbour-900: #272d3e;
  --color-misty-harbour-950: #151a27;
}

SCSS

$misty-harbour: #66749b;
$misty-harbour-rgb: 102, 116, 155;
$misty-harbour-light: mix(#fff, $misty-harbour, 20%);
$misty-harbour-dark: mix(#000, $misty-harbour, 20%);

.element {
  color: $misty-harbour;
  box-shadow: 0 0 0 2px rgba($misty-harbour, 0.35);
}