#6573A3

CSS

:root {
  --misty-harbour: #6573a3;
  --misty-harbour-rgb: 101 115 163;
  --misty-harbour-oklch: oklch(0.564 0.077 271.3);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(226 25% 52%);
  border-color: oklch(0.564 0.077 271.3);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #6573a3;
  --color-misty-harbour-50: #eef4ff;
  --color-misty-harbour-100: #dfe7ff;
  --color-misty-harbour-200: #c9d3f6;
  --color-misty-harbour-300: #aab5df;
  --color-misty-harbour-400: #8e9ccc;
  --color-misty-harbour-500: #7483b9;
  --color-misty-harbour-600: #626f9d;
  --color-misty-harbour-700: #4e597e;
  --color-misty-harbour-800: #38415d;
  --color-misty-harbour-900: #262d41;
  --color-misty-harbour-950: #141a2a;
}

SCSS

$misty-harbour: #6573a3;
$misty-harbour-rgb: 101, 115, 163;
$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);
}