#D0ECF0

CSS

:root {
  --castle-in-the-sky: #d0ecf0;
  --castle-in-the-sky-rgb: 208 236 240;
  --castle-in-the-sky-oklch: oklch(0.924 0.03 207.1);
}

.element {
  color: var(--castle-in-the-sky);
  background-color: hsl(187 52% 88%);
  border-color: oklch(0.924 0.03 207.1);
}

Tailwind CSS v4

@theme {
  --color-castle-in-the-sky: #d0ecf0;
  --color-castle-in-the-sky-50: #ecf8fa;
  --color-castle-in-the-sky-100: #ddebed;
  --color-castle-in-the-sky-200: #c6d8db;
  --color-castle-in-the-sky-300: #a7bcc0;
  --color-castle-in-the-sky-400: #8ba4a7;
  --color-castle-in-the-sky-500: #708c90;
  --color-castle-in-the-sky-600: #5f777a;
  --color-castle-in-the-sky-700: #4c5f62;
  --color-castle-in-the-sky-800: #374647;
  --color-castle-in-the-sky-900: #253031;
  --color-castle-in-the-sky-950: #141c1d;
}

SCSS

$castle-in-the-sky: #d0ecf0;
$castle-in-the-sky-rgb: 208, 236, 240;
$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);
}