#5F779F

CSS

:root {
  --misty-harbour: #5f779f;
  --misty-harbour-rgb: 95 119 159;
  --misty-harbour-oklch: oklch(0.566 0.068 260.4);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(218 25% 50%);
  border-color: oklch(0.566 0.068 260.4);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #5f779f;
  --color-misty-harbour-50: #ebf6ff;
  --color-misty-harbour-100: #dce9ff;
  --color-misty-harbour-200: #c5d5f2;
  --color-misty-harbour-300: #a5b8db;
  --color-misty-harbour-400: #879fc7;
  --color-misty-harbour-500: #6c87b4;
  --color-misty-harbour-600: #5c7298;
  --color-misty-harbour-700: #495b7a;
  --color-misty-harbour-800: #34435a;
  --color-misty-harbour-900: #232e3f;
  --color-misty-harbour-950: #121b28;
}

SCSS

$misty-harbour: #5f779f;
$misty-harbour-rgb: 95, 119, 159;
$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);
}