#5F75A1

CSS

:root {
  --misty-harbour: #5f75a1;
  --misty-harbour-rgb: 95 117 161;
  --misty-harbour-oklch: oklch(0.563 0.073 263.7);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(220 26% 50%);
  border-color: oklch(0.563 0.073 263.7);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #5f75a1;
  --color-misty-harbour-50: #ebf5ff;
  --color-misty-harbour-100: #dce8ff;
  --color-misty-harbour-200: #c5d4f5;
  --color-misty-harbour-300: #a6b7de;
  --color-misty-harbour-400: #889fcb;
  --color-misty-harbour-500: #6d86b7;
  --color-misty-harbour-600: #5d719b;
  --color-misty-harbour-700: #4a5b7c;
  --color-misty-harbour-800: #34435c;
  --color-misty-harbour-900: #242e40;
  --color-misty-harbour-950: #121b29;
}

SCSS

$misty-harbour: #5f75a1;
$misty-harbour-rgb: 95, 117, 161;
$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);
}