#3075CB

CSS

:root {
  --fading-night: #3075cb;
  --fading-night-rgb: 48 117 203;
  --fading-night-oklch: oklch(0.563 0.15 255.7);
}

.element {
  color: var(--fading-night);
  background-color: hsl(213 62% 49%);
  border-color: oklch(0.563 0.15 255.7);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #3075cb;
  --color-fading-night-50: #dbf7ff;
  --color-fading-night-100: #c9eaff;
  --color-fading-night-200: #acd7ff;
  --color-fading-night-300: #86b9ff;
  --color-fading-night-400: #5fa0f5;
  --color-fading-night-500: #3886e7;
  --color-fading-night-600: #3171c2;
  --color-fading-night-700: #275b9c;
  --color-fading-night-800: #164374;
  --color-fading-night-900: #0e2e52;
  --color-fading-night-950: #021b37;
}

SCSS

$fading-night: #3075cb;
$fading-night-rgb: 48, 117, 203;
$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);
}