#6666A3

CSS

:root {
  --twinkle-night: #6666a3;
  --twinkle-night-rgb: 102 102 163;
  --twinkle-night-oklch: oklch(0.537 0.095 282.7);
}

.element {
  color: var(--twinkle-night);
  background-color: hsl(240 25% 52%);
  border-color: oklch(0.537 0.095 282.7);
}

Tailwind CSS v4

@theme {
  --color-twinkle-night: #6666a3;
  --color-twinkle-night-50: #f1f2ff;
  --color-twinkle-night-100: #e4e4ff;
  --color-twinkle-night-200: #cfcffc;
  --color-twinkle-night-300: #b2b1e7;
  --color-twinkle-night-400: #9697d5;
  --color-twinkle-night-500: #7d7ec3;
  --color-twinkle-night-600: #6a6aa5;
  --color-twinkle-night-700: #555584;
  --color-twinkle-night-800: #3c3e62;
  --color-twinkle-night-900: #292b45;
  --color-twinkle-night-950: #17182d;
}

SCSS

$twinkle-night: #6666a3;
$twinkle-night-rgb: 102, 102, 163;
$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);
}