#2B75CA

CSS

:root {
  --fading-night: #2b75ca;
  --fading-night-rgb: 43 117 202;
  --fading-night-oklch: oklch(0.561 0.15 254.5);
}

.element {
  color: var(--fading-night);
  background-color: hsl(212 65% 48%);
  border-color: oklch(0.561 0.15 254.5);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #2b75ca;
  --color-fading-night-50: #daf8ff;
  --color-fading-night-100: #c8ebff;
  --color-fading-night-200: #abd7ff;
  --color-fading-night-300: #84baff;
  --color-fading-night-400: #5ca1f5;
  --color-fading-night-500: #3386e6;
  --color-fading-night-600: #2d72c2;
  --color-fading-night-700: #245b9c;
  --color-fading-night-800: #144374;
  --color-fading-night-900: #0d2f52;
  --color-fading-night-950: #011b37;
}

SCSS

$fading-night: #2b75ca;
$fading-night-rgb: 43, 117, 202;
$fading-night-light: mix(#fff, $fading-night, 20%);
$fading-night-dark: mix(#000, $fading-night, 20%);

.element {
  color: $fading-night;
  box-shadow: 0 0 0 2px rgba($fading-night, 0.35);
}