#63689C

CSS

:root {
  --twinkle-night: #63689c;
  --twinkle-night-rgb: 99 104 156;
  --twinkle-night-oklch: oklch(0.535 0.082 279);
}

.element {
  color: var(--twinkle-night);
  background-color: hsl(235 22% 50%);
  border-color: oklch(0.535 0.082 279);
}

Tailwind CSS v4

@theme {
  --color-twinkle-night: #63689c;
  --color-twinkle-night-50: #f0f3ff;
  --color-twinkle-night-100: #e2e5ff;
  --color-twinkle-night-200: #cdd1f7;
  --color-twinkle-night-300: #afb3e1;
  --color-twinkle-night-400: #949ace;
  --color-twinkle-night-500: #7a80bc;
  --color-twinkle-night-600: #686d9e;
  --color-twinkle-night-700: #53577f;
  --color-twinkle-night-800: #3b405f;
  --color-twinkle-night-900: #292c42;
  --color-twinkle-night-950: #16192b;
}

SCSS

$twinkle-night: #63689c;
$twinkle-night-rgb: 99, 104, 156;
$twinkle-night-light: mix(#fff, $twinkle-night, 20%);
$twinkle-night-dark: mix(#000, $twinkle-night, 20%);

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