#A9BBFF

CSS

:root {
  --pastel-blue: #a9bbff;
  --pastel-blue-rgb: 169 187 255;
  --pastel-blue-oklch: oklch(0.803 0.099 272.6);
}

.element {
  color: var(--pastel-blue);
  background-color: hsl(227 100% 83%);
  border-color: oklch(0.803 0.099 272.6);
}

Tailwind CSS v4

@theme {
  --color-pastel-blue: #a9bbff;
  --color-pastel-blue-50: #ecf4ff;
  --color-pastel-blue-100: #dde6ff;
  --color-pastel-blue-200: #c7d2ff;
  --color-pastel-blue-300: #a8b4ea;
  --color-pastel-blue-400: #8a9bd9;
  --color-pastel-blue-500: #7081c8;
  --color-pastel-blue-600: #5f6da8;
  --color-pastel-blue-700: #4c5787;
  --color-pastel-blue-800: #354065;
  --color-pastel-blue-900: #242c47;
  --color-pastel-blue-950: #13192e;
}

SCSS

$pastel-blue: #a9bbff;
$pastel-blue-rgb: 169, 187, 255;
$pastel-blue-light: mix(#fff, $pastel-blue, 20%);
$pastel-blue-dark: mix(#000, $pastel-blue, 20%);

.element {
  color: $pastel-blue;
  box-shadow: 0 0 0 2px rgba($pastel-blue, 0.35);
}