#D5ECEF

CSS

:root {
  --castle-in-the-sky: #d5ecef;
  --castle-in-the-sky-rgb: 213 236 239;
  --castle-in-the-sky-oklch: oklch(0.927 0.025 206.2);
}

.element {
  color: var(--castle-in-the-sky);
  background-color: hsl(187 45% 89%);
  border-color: oklch(0.927 0.025 206.2);
}

Tailwind CSS v4

@theme {
  --color-castle-in-the-sky: #d5ecef;
  --color-castle-in-the-sky-50: #eef7f9;
  --color-castle-in-the-sky-100: #dfeaec;
  --color-castle-in-the-sky-200: #c9d7da;
  --color-castle-in-the-sky-300: #aabbbe;
  --color-castle-in-the-sky-400: #8ea3a6;
  --color-castle-in-the-sky-500: #748b8e;
  --color-castle-in-the-sky-600: #627678;
  --color-castle-in-the-sky-700: #4e5e60;
  --color-castle-in-the-sky-800: #394546;
  --color-castle-in-the-sky-900: #273031;
  --color-castle-in-the-sky-950: #151c1d;
}

SCSS

$castle-in-the-sky: #d5ecef;
$castle-in-the-sky-rgb: 213, 236, 239;
$castle-in-the-sky-light: mix(#fff, $castle-in-the-sky, 20%);
$castle-in-the-sky-dark: mix(#000, $castle-in-the-sky, 20%);

.element {
  color: $castle-in-the-sky;
  box-shadow: 0 0 0 2px rgba($castle-in-the-sky, 0.35);
}