#43A5CC

CSS

:root {
  --mystic-blue: #43a5cc;
  --mystic-blue-rgb: 67 165 204;
  --mystic-blue-oklch: oklch(0.68 0.107 227.9);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(197 57% 53%);
  border-color: oklch(0.68 0.107 227.9);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #43a5cc;
  --color-mystic-blue-50: #d7fcff;
  --color-mystic-blue-100: #c4efff;
  --color-mystic-blue-200: #a5def9;
  --color-mystic-blue-300: #7cc2e4;
  --color-mystic-blue-400: #50abd0;
  --color-mystic-blue-500: #1293bd;
  --color-mystic-blue-600: #167ca0;
  --color-mystic-blue-700: #136480;
  --color-mystic-blue-800: #07495e;
  --color-mystic-blue-900: #063342;
  --color-mystic-blue-950: #001e2a;
}

SCSS

$mystic-blue: #43a5cc;
$mystic-blue-rgb: 67, 165, 204;
$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);
}