#6373A6

CSS

:root {
  --twinkle-night: #6373a6;
  --twinkle-night-rgb: 99 115 166;
  --twinkle-night-oklch: oklch(0.564 0.082 270.3);
}

.element {
  color: var(--twinkle-night);
  background-color: hsl(226 27% 52%);
  border-color: oklch(0.564 0.082 270.3);
}

Tailwind CSS v4

@theme {
  --color-twinkle-night: #6373a6;
  --color-twinkle-night-50: #edf4ff;
  --color-twinkle-night-100: #dee7ff;
  --color-twinkle-night-200: #c8d3f8;
  --color-twinkle-night-300: #a9b5e2;
  --color-twinkle-night-400: #8c9ccf;
  --color-twinkle-night-500: #7183bd;
  --color-twinkle-night-600: #606f9f;
  --color-twinkle-night-700: #4d5980;
  --color-twinkle-night-800: #36415f;
  --color-twinkle-night-900: #252d43;
  --color-twinkle-night-950: #141a2b;
}

SCSS

$twinkle-night: #6373a6;
$twinkle-night-rgb: 99, 115, 166;
$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);
}