#346FD2

CSS

:root {
  --fading-night: #346fd2;
  --fading-night-rgb: 52 111 210;
  --fading-night-oklch: oklch(0.556 0.165 260.1);
}

.element {
  color: var(--fading-night);
  background-color: hsl(218 64% 51%);
  border-color: oklch(0.556 0.165 260.1);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #346fd2;
  --color-fading-night-50: #dcf6ff;
  --color-fading-night-100: #cae9ff;
  --color-fading-night-200: #aed5ff;
  --color-fading-night-300: #89b7ff;
  --color-fading-night-400: #629dff;
  --color-fading-night-500: #3f81f1;
  --color-fading-night-600: #366ecb;
  --color-fading-night-700: #2b58a4;
  --color-fading-night-800: #19417a;
  --color-fading-night-900: #102d56;
  --color-fading-night-950: #04193a;
}

SCSS

$fading-night: #346fd2;
$fading-night-rgb: 52, 111, 210;
$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);
}