#677494

CSS

:root {
  --misty-harbour: #677494;
  --misty-harbour-rgb: 103 116 148;
  --misty-harbour-oklch: oklch(0.56 0.052 267.5);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(223 18% 49%);
  border-color: oklch(0.56 0.052 267.5);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #677494;
  --color-misty-harbour-50: #eff5ff;
  --color-misty-harbour-100: #e1e8fa;
  --color-misty-harbour-200: #cbd4eb;
  --color-misty-harbour-300: #acb7d3;
  --color-misty-harbour-400: #919ebe;
  --color-misty-harbour-500: #7786aa;
  --color-misty-harbour-600: #65718f;
  --color-misty-harbour-700: #505a73;
  --color-misty-harbour-800: #3a4255;
  --color-misty-harbour-900: #272e3b;
  --color-misty-harbour-950: #161a25;
}

SCSS

$misty-harbour: #677494;
$misty-harbour-rgb: 103, 116, 148;
$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);
}