#3774C9

CSS

:root {
  --fading-night: #3774c9;
  --fading-night-rgb: 55 116 201;
  --fading-night-oklch: oklch(0.562 0.146 257.3);
}

.element {
  color: var(--fading-night);
  background-color: hsl(215 57% 50%);
  border-color: oklch(0.562 0.146 257.3);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #3774c9;
  --color-fading-night-50: #ddf7ff;
  --color-fading-night-100: #cbeaff;
  --color-fading-night-200: #afd6ff;
  --color-fading-night-300: #8ab8ff;
  --color-fading-night-400: #649ff3;
  --color-fading-night-500: #4085e5;
  --color-fading-night-600: #3771c1;
  --color-fading-night-700: #2c5a9b;
  --color-fading-night-800: #1b4374;
  --color-fading-night-900: #112e51;
  --color-fading-night-950: #041a37;
}

SCSS

$fading-night: #3774c9;
$fading-night-rgb: 55, 116, 201;
$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);
}