#3F71D3

CSS

:root {
  --skies-of-cyberspace: #3f71d3;
  --skies-of-cyberspace-rgb: 63 113 211;
  --skies-of-cyberspace-oklch: oklch(0.565 0.16 262.2);
}

.element {
  color: var(--skies-of-cyberspace);
  background-color: hsl(220 63% 54%);
  border-color: oklch(0.565 0.16 262.2);
}

Tailwind CSS v4

@theme {
  --color-skies-of-cyberspace: #3f71d3;
  --color-skies-of-cyberspace-50: #def6ff;
  --color-skies-of-cyberspace-100: #cde8ff;
  --color-skies-of-cyberspace-200: #b2d4ff;
  --color-skies-of-cyberspace-300: #8eb6ff;
  --color-skies-of-cyberspace-400: #699cfc;
  --color-skies-of-cyberspace-500: #4880ef;
  --color-skies-of-cyberspace-600: #3e6dc9;
  --color-skies-of-cyberspace-700: #3157a2;
  --color-skies-of-cyberspace-800: #1f4079;
  --color-skies-of-cyberspace-900: #142c55;
  --color-skies-of-cyberspace-950: #06193a;
}

SCSS

$skies-of-cyberspace: #3f71d3;
$skies-of-cyberspace-rgb: 63, 113, 211;
$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);
}