#3372D7

CSS

:root {
  --fading-night: #3372d7;
  --fading-night-rgb: 51 114 215;
  --fading-night-oklch: oklch(0.566 0.168 259.6);
}

.element {
  color: var(--fading-night);
  background-color: hsl(217 67% 52%);
  border-color: oklch(0.566 0.168 259.6);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #3372d7;
  --color-fading-night-50: #dbf6ff;
  --color-fading-night-100: #c9e9ff;
  --color-fading-night-200: #acd5ff;
  --color-fading-night-300: #87b7ff;
  --color-fading-night-400: #5f9dff;
  --color-fading-night-500: #3b81f3;
  --color-fading-night-600: #336ecd;
  --color-fading-night-700: #2858a5;
  --color-fading-night-800: #17417b;
  --color-fading-night-900: #0f2d57;
  --color-fading-night-950: #03193b;
}

SCSS

$fading-night: #3372d7;
$fading-night-rgb: 51, 114, 215;
$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);
}