#59A3C8

CSS

:root {
  --mystic-blue: #59a3c8;
  --mystic-blue-rgb: 89 163 200;
  --mystic-blue-oklch: oklch(0.682 0.092 232);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(200 50% 57%);
  border-color: oklch(0.682 0.092 232);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #59a3c8;
  --color-mystic-blue-50: #ddfaff;
  --color-mystic-blue-100: #cbeeff;
  --color-mystic-blue-200: #aedcf6;
  --color-mystic-blue-300: #88c0e0;
  --color-mystic-blue-400: #63a8cb;
  --color-mystic-blue-500: #3b90b8;
  --color-mystic-blue-600: #347a9c;
  --color-mystic-blue-700: #29627d;
  --color-mystic-blue-800: #1a485c;
  --color-mystic-blue-900: #113240;
  --color-mystic-blue-950: #031e29;
}

SCSS

$mystic-blue: #59a3c8;
$mystic-blue-rgb: 89, 163, 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);
}