#99A6CE

CSS

:root {
  --old-world: #99a6ce;
  --old-world-rgb: 153 166 206;
  --old-world-oklch: oklch(0.729 0.06 270.8);
}

.element {
  color: var(--old-world);
  background-color: hsl(225 35% 70%);
  border-color: oklch(0.729 0.06 270.8);
}

Tailwind CSS v4

@theme {
  --color-old-world: #99a6ce;
  --color-old-world-50: #eff4ff;
  --color-old-world-100: #e1e7fd;
  --color-old-world-200: #cbd3ef;
  --color-old-world-300: #adb6d7;
  --color-old-world-400: #919dc3;
  --color-old-world-500: #7784af;
  --color-old-world-600: #657094;
  --color-old-world-700: #515a76;
  --color-old-world-800: #3a4258;
  --color-old-world-900: #272d3d;
  --color-old-world-950: #161a27;
}

SCSS

$old-world: #99a6ce;
$old-world-rgb: 153, 166, 206;
$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);
}