#657594

CSS

:root {
  --misty-harbour: #657594;
  --misty-harbour-rgb: 101 117 148;
  --misty-harbour-oklch: oklch(0.561 0.052 263.4);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(220 19% 49%);
  border-color: oklch(0.561 0.052 263.4);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #657594;
  --color-misty-harbour-50: #eef5ff;
  --color-misty-harbour-100: #e0e8fa;
  --color-misty-harbour-200: #cad4eb;
  --color-misty-harbour-300: #abb7d3;
  --color-misty-harbour-400: #8f9fbe;
  --color-misty-harbour-500: #7486a9;
  --color-misty-harbour-600: #63728f;
  --color-misty-harbour-700: #4f5b73;
  --color-misty-harbour-800: #384355;
  --color-misty-harbour-900: #272e3b;
  --color-misty-harbour-950: #151b25;
}

SCSS

$misty-harbour: #657594;
$misty-harbour-rgb: 101, 117, 148;
$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);
}