#677699

CSS

:root {
  --misty-harbour: #677699;
  --misty-harbour-rgb: 103 118 153;
  --misty-harbour-oklch: oklch(0.567 0.057 266.6);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(222 20% 50%);
  border-color: oklch(0.567 0.057 266.6);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #677699;
  --color-misty-harbour-50: #eef5ff;
  --color-misty-harbour-100: #e0e8fc;
  --color-misty-harbour-200: #cad4ee;
  --color-misty-harbour-300: #abb7d6;
  --color-misty-harbour-400: #8f9ec1;
  --color-misty-harbour-500: #7586ad;
  --color-misty-harbour-600: #637192;
  --color-misty-harbour-700: #4f5a75;
  --color-misty-harbour-800: #384257;
  --color-misty-harbour-900: #272e3c;
  --color-misty-harbour-950: #151a26;
}

SCSS

$misty-harbour: #677699;
$misty-harbour-rgb: 103, 118, 153;
$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);
}