#6A7699

CSS

:root {
  --misty-harbour: #6a7699;
  --misty-harbour-rgb: 106 118 153;
  --misty-harbour-oklch: oklch(0.569 0.056 269.9);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(225 19% 51%);
  border-color: oklch(0.569 0.056 269.9);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #6a7699;
  --color-misty-harbour-50: #eff5ff;
  --color-misty-harbour-100: #e1e7fb;
  --color-misty-harbour-200: #cbd3ed;
  --color-misty-harbour-300: #adb6d5;
  --color-misty-harbour-400: #919dc0;
  --color-misty-harbour-500: #7785ac;
  --color-misty-harbour-600: #657091;
  --color-misty-harbour-700: #515a75;
  --color-misty-harbour-800: #3a4256;
  --color-misty-harbour-900: #282d3c;
  --color-misty-harbour-950: #161a26;
}

SCSS

$misty-harbour: #6a7699;
$misty-harbour-rgb: 106, 118, 153;
$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);
}