#657692

CSS

:root {
  --misty-harbour: #657692;
  --misty-harbour-rgb: 101 118 146;
  --misty-harbour-oklch: oklch(0.563 0.048 260.3);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(217 18% 48%);
  border-color: oklch(0.563 0.048 260.3);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #657692;
  --color-misty-harbour-50: #eef6ff;
  --color-misty-harbour-100: #dfe8f9;
  --color-misty-harbour-200: #c9d5e9;
  --color-misty-harbour-300: #aab8d1;
  --color-misty-harbour-400: #8e9fbb;
  --color-misty-harbour-500: #7487a7;
  --color-misty-harbour-600: #62728d;
  --color-misty-harbour-700: #4e5b71;
  --color-misty-harbour-800: #384353;
  --color-misty-harbour-900: #262e3a;
  --color-misty-harbour-950: #151b24;
}

SCSS

$misty-harbour: #657692;
$misty-harbour-rgb: 101, 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);
}