#8FA5D2

CSS

:root {
  --old-world: #8fa5d2;
  --old-world-rgb: 143 165 210;
  --old-world-oklch: oklch(0.721 0.07 264.4);
}

.element {
  color: var(--old-world);
  background-color: hsl(220 43% 69%);
  border-color: oklch(0.721 0.07 264.4);
}

Tailwind CSS v4

@theme {
  --color-old-world: #8fa5d2;
  --color-old-world-50: #ecf5ff;
  --color-old-world-100: #dde8ff;
  --color-old-world-200: #c6d4f3;
  --color-old-world-300: #a7b7dc;
  --color-old-world-400: #8a9ec9;
  --color-old-world-500: #6f86b5;
  --color-old-world-600: #5e7199;
  --color-old-world-700: #4b5b7b;
  --color-old-world-800: #35425b;
  --color-old-world-900: #242e40;
  --color-old-world-950: #131b29;
}

SCSS

$old-world: #8fa5d2;
$old-world-rgb: 143, 165, 210;
$old-world-light: mix(#fff, $old-world, 20%);
$old-world-dark: mix(#000, $old-world, 20%);

.element {
  color: $old-world;
  box-shadow: 0 0 0 2px rgba($old-world, 0.35);
}