#1F78CF

CSS

:root {
  --fading-night: #1f78cf;
  --fading-night-rgb: 31 120 207;
  --fading-night-oklch: oklch(0.568 0.156 252.5);
}

.element {
  color: var(--fading-night);
  background-color: hsl(210 74% 47%);
  border-color: oklch(0.568 0.156 252.5);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #1f78cf;
  --color-fading-night-50: #d7f8ff;
  --color-fading-night-100: #c5ebff;
  --color-fading-night-200: #a6d8ff;
  --color-fading-night-300: #7ebbff;
  --color-fading-night-400: #53a2f7;
  --color-fading-night-500: #2387e9;
  --color-fading-night-600: #2073c5;
  --color-fading-night-700: #1a5c9e;
  --color-fading-night-800: #0a4476;
  --color-fading-night-900: #072f53;
  --color-fading-night-950: #001b38;
}

SCSS

$fading-night: #1f78cf;
$fading-night-rgb: 31, 120, 207;
$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);
}