#2D73D5

CSS

:root {
  --fading-night: #2d73d5;
  --fading-night-rgb: 45 115 213;
  --fading-night-oklch: oklch(0.565 0.166 257.7);
}

.element {
  color: var(--fading-night);
  background-color: hsl(215 67% 51%);
  border-color: oklch(0.565 0.166 257.7);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #2d73d5;
  --color-fading-night-50: #daf7ff;
  --color-fading-night-100: #c8eaff;
  --color-fading-night-200: #aad6ff;
  --color-fading-night-300: #84b8ff;
  --color-fading-night-400: #5c9eff;
  --color-fading-night-500: #3483f1;
  --color-fading-night-600: #2e6fcb;
  --color-fading-night-700: #2459a4;
  --color-fading-night-800: #13427a;
  --color-fading-night-900: #0c2d56;
  --color-fading-night-950: #011a3a;
}

SCSS

$fading-night: #2d73d5;
$fading-night-rgb: 45, 115, 213;
$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);
}