#3F73D5

CSS

:root {
  --skies-of-cyberspace: #3f73d5;
  --skies-of-cyberspace-rgb: 63 115 213;
  --skies-of-cyberspace-oklch: oklch(0.571 0.161 261.7);
}

.element {
  color: var(--skies-of-cyberspace);
  background-color: hsl(219 64% 54%);
  border-color: oklch(0.571 0.161 261.7);
}

Tailwind CSS v4

@theme {
  --color-skies-of-cyberspace: #3f73d5;
  --color-skies-of-cyberspace-50: #def6ff;
  --color-skies-of-cyberspace-100: #cde8ff;
  --color-skies-of-cyberspace-200: #b1d4ff;
  --color-skies-of-cyberspace-300: #8db6ff;
  --color-skies-of-cyberspace-400: #689cfd;
  --color-skies-of-cyberspace-500: #4681ef;
  --color-skies-of-cyberspace-600: #3c6dc9;
  --color-skies-of-cyberspace-700: #3057a2;
  --color-skies-of-cyberspace-800: #1e4079;
  --color-skies-of-cyberspace-900: #132d55;
  --color-skies-of-cyberspace-950: #06193a;
}

SCSS

$skies-of-cyberspace: #3f73d5;
$skies-of-cyberspace-rgb: 63, 115, 213;
$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);
}