#6376A4

CSS

:root {
  --misty-harbour: #6376a4;
  --misty-harbour-rgb: 99 118 164;
  --misty-harbour-oklch: oklch(0.569 0.075 266.8);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(222 26% 52%);
  border-color: oklch(0.569 0.075 266.8);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #6376a4;
  --color-misty-harbour-50: #ecf5ff;
  --color-misty-harbour-100: #dde8ff;
  --color-misty-harbour-200: #c7d4f5;
  --color-misty-harbour-300: #a7b7df;
  --color-misty-harbour-400: #8a9ecc;
  --color-misty-harbour-500: #6f85b9;
  --color-misty-harbour-600: #5f709c;
  --color-misty-harbour-700: #4b5a7d;
  --color-misty-harbour-800: #35425d;
  --color-misty-harbour-900: #242e41;
  --color-misty-harbour-950: #131a2a;
}

SCSS

$misty-harbour: #6376a4;
$misty-harbour-rgb: 99, 118, 164;
$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);
}