#64749D

CSS

:root {
  --misty-harbour: #64749d;
  --misty-harbour-rgb: 100 116 157;
  --misty-harbour-oklch: oklch(0.562 0.067 267.8);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(223 23% 50%);
  border-color: oklch(0.562 0.067 267.8);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #64749d;
  --color-misty-harbour-50: #edf5ff;
  --color-misty-harbour-100: #dfe7ff;
  --color-misty-harbour-200: #c9d4f2;
  --color-misty-harbour-300: #aab6da;
  --color-misty-harbour-400: #8d9ec7;
  --color-misty-harbour-500: #7385b3;
  --color-misty-harbour-600: #617197;
  --color-misty-harbour-700: #4e5a79;
  --color-misty-harbour-800: #37425a;
  --color-misty-harbour-900: #262e3f;
  --color-misty-harbour-950: #141a28;
}

SCSS

$misty-harbour: #64749d;
$misty-harbour-rgb: 100, 116, 157;
$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);
}