#6F71AF

CSS

:root {
  --twinkle-night: #6f71af;
  --twinkle-night-rgb: 111 113 175;
  --twinkle-night-oklch: oklch(0.573 0.095 281.5);
}

.element {
  color: var(--twinkle-night);
  background-color: hsl(238 29% 56%);
  border-color: oklch(0.573 0.095 281.5);
}

Tailwind CSS v4

@theme {
  --color-twinkle-night: #6f71af;
  --color-twinkle-night-50: #f1f2ff;
  --color-twinkle-night-100: #e3e4ff;
  --color-twinkle-night-200: #ced0fc;
  --color-twinkle-night-300: #b0b2e7;
  --color-twinkle-night-400: #9598d6;
  --color-twinkle-night-500: #7c7ec4;
  --color-twinkle-night-600: #696ba5;
  --color-twinkle-night-700: #545584;
  --color-twinkle-night-800: #3c3f63;
  --color-twinkle-night-900: #292b45;
  --color-twinkle-night-950: #17182d;
}

SCSS

$twinkle-night: #6f71af;
$twinkle-night-rgb: 111, 113, 175;
$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);
}