#6A739A

CSS

:root {
  --misty-harbour: #6a739a;
  --misty-harbour-rgb: 106 115 154;
  --misty-harbour-oklch: oklch(0.563 0.061 274.2);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(229 19% 51%);
  border-color: oklch(0.563 0.061 274.2);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #6a739a;
  --color-misty-harbour-50: #f0f4ff;
  --color-misty-harbour-100: #e2e7fd;
  --color-misty-harbour-200: #cdd3ef;
  --color-misty-harbour-300: #aeb5d7;
  --color-misty-harbour-400: #939cc3;
  --color-misty-harbour-500: #7983af;
  --color-misty-harbour-600: #676f94;
  --color-misty-harbour-700: #525977;
  --color-misty-harbour-800: #3b4158;
  --color-misty-harbour-900: #282d3d;
  --color-misty-harbour-950: #161a27;
}

SCSS

$misty-harbour: #6a739a;
$misty-harbour-rgb: 106, 115, 154;
$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);
}