#5EAACE

CSS

:root {
  --mystic-blue: #5eaace;
  --mystic-blue-rgb: 94 170 206;
  --mystic-blue-oklch: oklch(0.703 0.092 230.5);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(199 53% 59%);
  border-color: oklch(0.703 0.092 230.5);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #5eaace;
  --color-mystic-blue-50: #dcfaff;
  --color-mystic-blue-100: #caeeff;
  --color-mystic-blue-200: #aedcf5;
  --color-mystic-blue-300: #87c0df;
  --color-mystic-blue-400: #61a9cb;
  --color-mystic-blue-500: #3991b8;
  --color-mystic-blue-600: #327b9b;
  --color-mystic-blue-700: #28627c;
  --color-mystic-blue-800: #19485c;
  --color-mystic-blue-900: #113240;
  --color-mystic-blue-950: #031e29;
}

SCSS

$mystic-blue: #5eaace;
$mystic-blue-rgb: 94, 170, 206;
$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);
}