#6375A6

CSS

:root {
  --misty-harbour: #6375a6;
  --misty-harbour-rgb: 99 117 166;
  --misty-harbour-oklch: oklch(0.568 0.079 268.4);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(224 27% 52%);
  border-color: oklch(0.568 0.079 268.4);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #6375a6;
  --color-misty-harbour-50: #ecf5ff;
  --color-misty-harbour-100: #dde7ff;
  --color-misty-harbour-200: #c7d3f7;
  --color-misty-harbour-300: #a8b6e1;
  --color-misty-harbour-400: #8b9dce;
  --color-misty-harbour-500: #7084bb;
  --color-misty-harbour-600: #5f709e;
  --color-misty-harbour-700: #4c597f;
  --color-misty-harbour-800: #36425e;
  --color-misty-harbour-900: #252d42;
  --color-misty-harbour-950: #131a2a;
}

SCSS

$misty-harbour: #6375a6;
$misty-harbour-rgb: 99, 117, 166;
$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);
}