#657597

CSS

:root {
  --misty-harbour: #657597;
  --misty-harbour-rgb: 101 117 151;
  --misty-harbour-oklch: oklch(0.563 0.056 265);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(221 20% 49%);
  border-color: oklch(0.563 0.056 265);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #657597;
  --color-misty-harbour-50: #eef5ff;
  --color-misty-harbour-100: #dfe8fb;
  --color-misty-harbour-200: #c9d4ed;
  --color-misty-harbour-300: #aab7d5;
  --color-misty-harbour-400: #8e9ec1;
  --color-misty-harbour-500: #7486ac;
  --color-misty-harbour-600: #627192;
  --color-misty-harbour-700: #4e5b75;
  --color-misty-harbour-800: #384256;
  --color-misty-harbour-900: #262e3c;
  --color-misty-harbour-950: #151b26;
}

SCSS

$misty-harbour: #657597;
$misty-harbour-rgb: 101, 117, 151;
$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);
}