#637692

CSS

:root {
  --misty-harbour: #637692;
  --misty-harbour-rgb: 99 118 146;
  --misty-harbour-oklch: oklch(0.561 0.049 258);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(216 19% 48%);
  border-color: oklch(0.561 0.049 258);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #637692;
  --color-misty-harbour-50: #edf6ff;
  --color-misty-harbour-100: #dee9f9;
  --color-misty-harbour-200: #c8d5ea;
  --color-misty-harbour-300: #a9b8d1;
  --color-misty-harbour-400: #8da0bc;
  --color-misty-harbour-500: #7288a7;
  --color-misty-harbour-600: #61738d;
  --color-misty-harbour-700: #4d5c71;
  --color-misty-harbour-800: #374353;
  --color-misty-harbour-900: #262e3a;
  --color-misty-harbour-950: #141b24;
}

SCSS

$misty-harbour: #637692;
$misty-harbour-rgb: 99, 118, 146;
$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);
}