#40A5D3

CSS

:root {
  --mystic-blue: #40a5d3;
  --mystic-blue-rgb: 64 165 211;
  --mystic-blue-oklch: oklch(0.683 0.114 231.7);
}

.element {
  color: var(--mystic-blue);
  background-color: hsl(199 63% 54%);
  border-color: oklch(0.683 0.114 231.7);
}

Tailwind CSS v4

@theme {
  --color-mystic-blue: #40a5d3;
  --color-mystic-blue-50: #d6fcff;
  --color-mystic-blue-100: #c3efff;
  --color-mystic-blue-200: #a4ddfe;
  --color-mystic-blue-300: #7ac2e9;
  --color-mystic-blue-400: #4daad6;
  --color-mystic-blue-500: #0392c4;
  --color-mystic-blue-600: #0e7ca5;
  --color-mystic-blue-700: #0d6385;
  --color-mystic-blue-800: #034962;
  --color-mystic-blue-900: #033345;
  --color-mystic-blue-950: #001e2c;
}

SCSS

$mystic-blue: #40a5d3;
$mystic-blue-rgb: 64, 165, 211;
$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);
}