#43A5D1

CSS

:root {
  --mystic-blue: #43a5d1;
  --mystic-blue-rgb: 67 165 209;
  --mystic-blue-oklch: oklch(0.683 0.111 231);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(199 61% 54%);
  border-color: oklch(0.683 0.111 231);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #43a5d1;
  --color-mystic-blue-50: #d7fbff;
  --color-mystic-blue-100: #c4efff;
  --color-mystic-blue-200: #a5ddfc;
  --color-mystic-blue-300: #7bc1e7;
  --color-mystic-blue-400: #50aad4;
  --color-mystic-blue-500: #1092c2;
  --color-mystic-blue-600: #157ca4;
  --color-mystic-blue-700: #126383;
  --color-mystic-blue-800: #064961;
  --color-mystic-blue-900: #053344;
  --color-mystic-blue-950: #001e2c;
}

SCSS

$mystic-blue: #43a5d1;
$mystic-blue-rgb: 67, 165, 209;
$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);
}