#3971D6

CSS

:root {
  --skies-of-cyberspace: #3971d6;
  --skies-of-cyberspace-rgb: 57 113 214;
  --skies-of-cyberspace-oklch: oklch(0.565 0.166 261.1);
}

.element {
  color: var(--skies-of-cyberspace);
  background-color: hsl(219 66% 53%);
  border-color: oklch(0.565 0.166 261.1);
}

Tailwind CSS v4

@theme {
  --color-skies-of-cyberspace: #3971d6;
  --color-skies-of-cyberspace-50: #dcf6ff;
  --color-skies-of-cyberspace-100: #cbe8ff;
  --color-skies-of-cyberspace-200: #afd4ff;
  --color-skies-of-cyberspace-300: #8ab6ff;
  --color-skies-of-cyberspace-400: #649cff;
  --color-skies-of-cyberspace-500: #4281f2;
  --color-skies-of-cyberspace-600: #386dcc;
  --color-skies-of-cyberspace-700: #2d57a4;
  --color-skies-of-cyberspace-800: #1b407b;
  --color-skies-of-cyberspace-900: #112d57;
  --color-skies-of-cyberspace-950: #04193b;
}

SCSS

$skies-of-cyberspace: #3971d6;
$skies-of-cyberspace-rgb: 57, 113, 214;
$skies-of-cyberspace-light: mix(#fff, $skies-of-cyberspace, 20%);
$skies-of-cyberspace-dark: mix(#000, $skies-of-cyberspace, 20%);

.element {
  color: $skies-of-cyberspace;
  box-shadow: 0 0 0 2px rgba($skies-of-cyberspace, 0.35);
}