#576B9D

CSS

:root {
  --twinkle-night: #576b9d;
  --twinkle-night-rgb: 87 107 157;
  --twinkle-night-oklch: oklch(0.533 0.083 267);
}

.element {
  color: var(--twinkle-night);
  background-color: hsl(223 29% 48%);
  border-color: oklch(0.533 0.083 267);
}

Tailwind CSS v4

@theme {
  --color-twinkle-night: #576b9d;
  --color-twinkle-night-50: #ebf5ff;
  --color-twinkle-night-100: #dce7ff;
  --color-twinkle-night-200: #c6d4f9;
  --color-twinkle-night-300: #a6b6e3;
  --color-twinkle-night-400: #889dd0;
  --color-twinkle-night-500: #6d84bd;
  --color-twinkle-night-600: #5d70a0;
  --color-twinkle-night-700: #4a5a80;
  --color-twinkle-night-800: #34425f;
  --color-twinkle-night-900: #242d43;
  --color-twinkle-night-950: #121a2b;
}

SCSS

$twinkle-night: #576b9d;
$twinkle-night-rgb: 87, 107, 157;
$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);
}