#617696

CSS

:root {
  --misty-harbour: #617696;
  --misty-harbour-rgb: 97 118 150;
  --misty-harbour-oklch: oklch(0.561 0.056 258.7);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(216 21% 48%);
  border-color: oklch(0.561 0.056 258.7);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #617696;
  --color-misty-harbour-50: #ecf6ff;
  --color-misty-harbour-100: #dde9fb;
  --color-misty-harbour-200: #c7d5ed;
  --color-misty-harbour-300: #a7b8d5;
  --color-misty-harbour-400: #8ba0c0;
  --color-misty-harbour-500: #7087ac;
  --color-misty-harbour-600: #5f7391;
  --color-misty-harbour-700: #4c5c74;
  --color-misty-harbour-800: #364356;
  --color-misty-harbour-900: #252e3c;
  --color-misty-harbour-950: #131b26;
}

SCSS

$misty-harbour: #617696;
$misty-harbour-rgb: 97, 118, 150;
$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);
}