#6376A1

CSS

:root {
  --misty-harbour: #6376a1;
  --misty-harbour-rgb: 99 118 161;
  --misty-harbour-oklch: oklch(0.568 0.071 265.8);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(222 25% 51%);
  border-color: oklch(0.568 0.071 265.8);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #6376a1;
  --color-misty-harbour-50: #ecf5ff;
  --color-misty-harbour-100: #dee8ff;
  --color-misty-harbour-200: #c7d4f3;
  --color-misty-harbour-300: #a8b7dd;
  --color-misty-harbour-400: #8b9ec9;
  --color-misty-harbour-500: #7085b6;
  --color-misty-harbour-600: #5f7199;
  --color-misty-harbour-700: #4c5a7b;
  --color-misty-harbour-800: #36425b;
  --color-misty-harbour-900: #252e40;
  --color-misty-harbour-950: #131a29;
}

SCSS

$misty-harbour: #6376a1;
$misty-harbour-rgb: 99, 118, 161;
$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);
}