#2976CA

CSS

:root {
  --fading-night: #2976ca;
  --fading-night-rgb: 41 118 202;
  --fading-night-oklch: oklch(0.563 0.15 253.7);
}

.element {
  color: var(--fading-night);
  background-color: hsl(211 66% 48%);
  border-color: oklch(0.563 0.15 253.7);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #2976ca;
  --color-fading-night-50: #d9f8ff;
  --color-fading-night-100: #c7ebff;
  --color-fading-night-200: #aad7ff;
  --color-fading-night-300: #83baff;
  --color-fading-night-400: #5aa1f4;
  --color-fading-night-500: #3087e6;
  --color-fading-night-600: #2b72c2;
  --color-fading-night-700: #225c9c;
  --color-fading-night-800: #124474;
  --color-fading-night-900: #0c2f52;
  --color-fading-night-950: #011b37;
}

SCSS

$fading-night: #2976ca;
$fading-night-rgb: 41, 118, 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);
}