#607599

CSS

:root {
  --misty-harbour: #607599;
  --misty-harbour-rgb: 96 117 153;
  --misty-harbour-oklch: oklch(0.56 0.062 261);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(218 23% 49%);
  border-color: oklch(0.56 0.062 261);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #607599;
  --color-misty-harbour-50: #ecf6ff;
  --color-misty-harbour-100: #dde8fd;
  --color-misty-harbour-200: #c7d5ef;
  --color-misty-harbour-300: #a7b8d8;
  --color-misty-harbour-400: #8a9fc3;
  --color-misty-harbour-500: #6f87af;
  --color-misty-harbour-600: #5e7294;
  --color-misty-harbour-700: #4b5b77;
  --color-misty-harbour-800: #364358;
  --color-misty-harbour-900: #242e3d;
  --color-misty-harbour-950: #131b27;
}

SCSS

$misty-harbour: #607599;
$misty-harbour-rgb: 96, 117, 153;
$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);
}