#31A6D4

CSS

:root {
  --mystic-blue: #31a6d4;
  --mystic-blue-rgb: 49 166 212;
  --mystic-blue-oklch: oklch(0.682 0.12 229.4);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(197 65% 51%);
  border-color: oklch(0.682 0.12 229.4);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #31a6d4;
  --color-mystic-blue-50: #d4fcff;
  --color-mystic-blue-100: #c0f0ff;
  --color-mystic-blue-200: #9fdeff;
  --color-mystic-blue-300: #73c3ea;
  --color-mystic-blue-400: #42abd7;
  --color-mystic-blue-500: #0093c5;
  --color-mystic-blue-600: #007da7;
  --color-mystic-blue-700: #006486;
  --color-mystic-blue-800: #004a63;
  --color-mystic-blue-900: #003345;
  --color-mystic-blue-950: #001f2d;
}

SCSS

$mystic-blue: #31a6d4;
$mystic-blue-rgb: 49, 166, 212;
$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);
}