#3175D4

CSS

:root {
  --fading-night: #3175d4;
  --fading-night-rgb: 49 117 212;
  --fading-night-oklch: oklch(0.569 0.161 257.6);
}

.element {
  color: var(--fading-night);
  background-color: hsl(215 65% 51%);
  border-color: oklch(0.569 0.161 257.6);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #3175d4;
  --color-fading-night-50: #daf7ff;
  --color-fading-night-100: #c8eaff;
  --color-fading-night-200: #abd6ff;
  --color-fading-night-300: #85b8ff;
  --color-fading-night-400: #5e9ffc;
  --color-fading-night-500: #3784ee;
  --color-fading-night-600: #3070c9;
  --color-fading-night-700: #2659a2;
  --color-fading-night-800: #154279;
  --color-fading-night-900: #0e2e55;
  --color-fading-night-950: #021a39;
}

SCSS

$fading-night: #3175d4;
$fading-night-rgb: 49, 117, 212;
$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);
}