#3FA5CE

CSS

:root {
  --mystic-blue: #3fa5ce;
  --mystic-blue-rgb: 63 165 206;
  --mystic-blue-oklch: oklch(0.68 0.11 228.5);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(197 59% 53%);
  border-color: oklch(0.68 0.11 228.5);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #3fa5ce;
  --color-mystic-blue-50: #d6fcff;
  --color-mystic-blue-100: #c3f0ff;
  --color-mystic-blue-200: #a4defb;
  --color-mystic-blue-300: #7ac2e5;
  --color-mystic-blue-400: #4dabd2;
  --color-mystic-blue-500: #0293c0;
  --color-mystic-blue-600: #0e7ca2;
  --color-mystic-blue-700: #0d6482;
  --color-mystic-blue-800: #034a60;
  --color-mystic-blue-900: #043343;
  --color-mystic-blue-950: #001f2b;
}

SCSS

$mystic-blue: #3fa5ce;
$mystic-blue-rgb: 63, 165, 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);
}