#4DA5C9

CSS

:root {
  --mystic-blue: #4da5c9;
  --mystic-blue-rgb: 77 165 201;
  --mystic-blue-oklch: oklch(0.682 0.099 227.8);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(197 53% 55%);
  border-color: oklch(0.682 0.099 227.8);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #4da5c9;
  --color-mystic-blue-50: #d9fbff;
  --color-mystic-blue-100: #c7efff;
  --color-mystic-blue-200: #a9ddf7;
  --color-mystic-blue-300: #81c1e0;
  --color-mystic-blue-400: #58aacc;
  --color-mystic-blue-500: #2792b9;
  --color-mystic-blue-600: #257c9d;
  --color-mystic-blue-700: #1d637e;
  --color-mystic-blue-800: #11495c;
  --color-mystic-blue-900: #0b3341;
  --color-mystic-blue-950: #001e29;
}

SCSS

$mystic-blue: #4da5c9;
$mystic-blue-rgb: 77, 165, 201;
$mystic-blue-light: mix(#fff, $mystic-blue, 20%);
$mystic-blue-dark: mix(#000, $mystic-blue, 20%);

.element {
  color: $mystic-blue;
  box-shadow: 0 0 0 2px rgba($mystic-blue, 0.35);
}