#57A3C9

CSS

:root {
  --mystic-blue: #57a3c9;
  --mystic-blue-rgb: 87 163 201;
  --mystic-blue-oklch: oklch(0.682 0.094 232.2);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(200 51% 56%);
  border-color: oklch(0.682 0.094 232.2);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #57a3c9;
  --color-mystic-blue-50: #dcfaff;
  --color-mystic-blue-100: #caeeff;
  --color-mystic-blue-200: #addcf7;
  --color-mystic-blue-300: #87c0e1;
  --color-mystic-blue-400: #61a8cd;
  --color-mystic-blue-500: #3891ba;
  --color-mystic-blue-600: #317a9d;
  --color-mystic-blue-700: #27627e;
  --color-mystic-blue-800: #19485d;
  --color-mystic-blue-900: #103241;
  --color-mystic-blue-950: #031e29;
}

SCSS

$mystic-blue: #57a3c9;
$mystic-blue-rgb: 87, 163, 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);
}