#91A2C4

CSS

:root {
  --old-world: #91a2c4;
  --old-world-rgb: 145 162 196;
  --old-world-oklch: oklch(0.711 0.053 264.2);
}

.element {
  color: var(--old-world);
  background-color: hsl(220 30% 67%);
  border-color: oklch(0.711 0.053 264.2);
}

Tailwind CSS v4

@theme {
  --color-old-world: #91a2c4;
  --color-old-world-50: #eef5ff;
  --color-old-world-100: #e0e8fa;
  --color-old-world-200: #cad4ec;
  --color-old-world-300: #abb7d4;
  --color-old-world-400: #8f9fbf;
  --color-old-world-500: #7486aa;
  --color-old-world-600: #637290;
  --color-old-world-700: #4f5b73;
  --color-old-world-800: #384355;
  --color-old-world-900: #272e3b;
  --color-old-world-950: #151b25;
}

SCSS

$old-world: #91a2c4;
$old-world-rgb: 145, 162, 196;
$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);
}