#616999

CSS

:root {
  --twinkle-night: #616999;
  --twinkle-night-rgb: 97 105 153;
  --twinkle-night-oklch: oklch(0.534 0.076 276.3);
}

.element {
  color: var(--twinkle-night);
  background-color: hsl(231 22% 49%);
  border-color: oklch(0.534 0.076 276.3);
}

Tailwind CSS v4

@theme {
  --color-twinkle-night: #616999;
  --color-twinkle-night-50: #f0f4ff;
  --color-twinkle-night-100: #e1e6ff;
  --color-twinkle-night-200: #ccd2f5;
  --color-twinkle-night-300: #aeb4df;
  --color-twinkle-night-400: #929bcc;
  --color-twinkle-night-500: #7882b9;
  --color-twinkle-night-600: #666e9c;
  --color-twinkle-night-700: #51587d;
  --color-twinkle-night-800: #3a405d;
  --color-twinkle-night-900: #282c41;
  --color-twinkle-night-950: #16192a;
}

SCSS

$twinkle-night: #616999;
$twinkle-night-rgb: 97, 105, 153;
$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);
}