#35A5D4

CSS

:root {
  --mystic-blue: #35a5d4;
  --mystic-blue-rgb: 53 165 212;
  --mystic-blue-oklch: oklch(0.68 0.119 230.6);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(198 65% 52%);
  border-color: oklch(0.68 0.119 230.6);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #35a5d4;
  --color-mystic-blue-50: #d4fcff;
  --color-mystic-blue-100: #c1f0ff;
  --color-mystic-blue-200: #a0deff;
  --color-mystic-blue-300: #75c2ea;
  --color-mystic-blue-400: #45abd8;
  --color-mystic-blue-500: #0093c6;
  --color-mystic-blue-600: #007ca7;
  --color-mystic-blue-700: #006486;
  --color-mystic-blue-800: #004a63;
  --color-mystic-blue-900: #003345;
  --color-mystic-blue-950: #001e2d;
}

SCSS

$mystic-blue: #35a5d4;
$mystic-blue-rgb: 53, 165, 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);
}