#3174D0

CSS

:root {
  --fading-night: #3174d0;
  --fading-night-rgb: 49 116 208;
  --fading-night-oklch: oklch(0.565 0.157 257.3);
}

.element {
  color: var(--fading-night);
  background-color: hsl(215 63% 50%);
  border-color: oklch(0.565 0.157 257.3);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #3174d0;
  --color-fading-night-50: #dbf7ff;
  --color-fading-night-100: #c9eaff;
  --color-fading-night-200: #acd6ff;
  --color-fading-night-300: #86b8ff;
  --color-fading-night-400: #5f9ffa;
  --color-fading-night-500: #3984ec;
  --color-fading-night-600: #3170c7;
  --color-fading-night-700: #275aa0;
  --color-fading-night-800: #164277;
  --color-fading-night-900: #0e2e54;
  --color-fading-night-950: #021a39;
}

SCSS

$fading-night: #3174d0;
$fading-night-rgb: 49, 116, 208;
$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);
}