#63749F

CSS

:root {
  --misty-harbour: #63749f;
  --misty-harbour-rgb: 99 116 159;
  --misty-harbour-oklch: oklch(0.562 0.07 267.5);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(223 24% 51%);
  border-color: oklch(0.562 0.07 267.5);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #63749f;
  --color-misty-harbour-50: #edf5ff;
  --color-misty-harbour-100: #dee7ff;
  --color-misty-harbour-200: #c8d4f3;
  --color-misty-harbour-300: #a9b6dc;
  --color-misty-harbour-400: #8c9ec9;
  --color-misty-harbour-500: #7285b5;
  --color-misty-harbour-600: #607099;
  --color-misty-harbour-700: #4d5a7b;
  --color-misty-harbour-800: #37425b;
  --color-misty-harbour-900: #252e40;
  --color-misty-harbour-950: #141a29;
}

SCSS

$misty-harbour: #63749f;
$misty-harbour-rgb: 99, 116, 159;
$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);
}