#56A4C8

CSS

:root {
  --mystic-blue: #56a4c8;
  --mystic-blue-rgb: 86 164 200;
  --mystic-blue-oklch: oklch(0.683 0.093 230.2);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(199 51% 56%);
  border-color: oklch(0.683 0.093 230.2);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #56a4c8;
  --color-mystic-blue-50: #dcfbff;
  --color-mystic-blue-100: #caeeff;
  --color-mystic-blue-200: #addcf6;
  --color-mystic-blue-300: #86c0df;
  --color-mystic-blue-400: #60a9cb;
  --color-mystic-blue-500: #3691b8;
  --color-mystic-blue-600: #307b9b;
  --color-mystic-blue-700: #26627d;
  --color-mystic-blue-800: #18485c;
  --color-mystic-blue-900: #103240;
  --color-mystic-blue-950: #021e29;
}

SCSS

$mystic-blue: #56a4c8;
$mystic-blue-rgb: 86, 164, 200;
$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);
}