#6573A1

CSS

:root {
  --misty-harbour: #6573a1;
  --misty-harbour-rgb: 101 115 161;
  --misty-harbour-oklch: oklch(0.563 0.074 270.9);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(226 24% 51%);
  border-color: oklch(0.563 0.074 270.9);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #6573a1;
  --color-misty-harbour-50: #eef4ff;
  --color-misty-harbour-100: #dfe7ff;
  --color-misty-harbour-200: #c9d3f5;
  --color-misty-harbour-300: #aab6de;
  --color-misty-harbour-400: #8e9dcb;
  --color-misty-harbour-500: #7484b7;
  --color-misty-harbour-600: #626f9b;
  --color-misty-harbour-700: #4e597c;
  --color-misty-harbour-800: #38415c;
  --color-misty-harbour-900: #262d41;
  --color-misty-harbour-950: #151a29;
}

SCSS

$misty-harbour: #6573a1;
$misty-harbour-rgb: 101, 115, 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);
}