#D7ECEE

CSS

:root {
  --castle-in-the-sky: #d7ecee;
  --castle-in-the-sky-rgb: 215 236 238;
  --castle-in-the-sky-oklch: oklch(0.928 0.022 203.7);
}

.element {
  color: var(--castle-in-the-sky);
  background-color: hsl(185 40% 89%);
  border-color: oklch(0.928 0.022 203.7);
}

Tailwind CSS v4

@theme {
  --color-castle-in-the-sky: #d7ecee;
  --color-castle-in-the-sky-50: #eef7f8;
  --color-castle-in-the-sky-100: #e0eaeb;
  --color-castle-in-the-sky-200: #cad7d9;
  --color-castle-in-the-sky-300: #abbbbd;
  --color-castle-in-the-sky-400: #90a3a4;
  --color-castle-in-the-sky-500: #768b8d;
  --color-castle-in-the-sky-600: #647577;
  --color-castle-in-the-sky-700: #505e5f;
  --color-castle-in-the-sky-800: #3a4546;
  --color-castle-in-the-sky-900: #283030;
  --color-castle-in-the-sky-950: #161c1c;
}

SCSS

$castle-in-the-sky: #d7ecee;
$castle-in-the-sky-rgb: 215, 236, 238;
$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);
}