#5F759C

CSS

:root {
  --misty-harbour: #5f759c;
  --misty-harbour-rgb: 95 117 156;
  --misty-harbour-oklch: oklch(0.561 0.066 261.6);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(218 24% 49%);
  border-color: oklch(0.561 0.066 261.6);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #5f759c;
  --color-misty-harbour-50: #ebf6ff;
  --color-misty-harbour-100: #dde8ff;
  --color-misty-harbour-200: #c6d5f1;
  --color-misty-harbour-300: #a6b8da;
  --color-misty-harbour-400: #899fc6;
  --color-misty-harbour-500: #6e87b3;
  --color-misty-harbour-600: #5d7297;
  --color-misty-harbour-700: #4a5b79;
  --color-misty-harbour-800: #35435a;
  --color-misty-harbour-900: #242e3f;
  --color-misty-harbour-950: #131b28;
}

SCSS

$misty-harbour: #5f759c;
$misty-harbour-rgb: 95, 117, 156;
$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);
}