#1675D2

CSS

:root {
  --fading-night: #1675d2;
  --fading-night-rgb: 22 117 210;
  --fading-night-oklch: oklch(0.562 0.165 253.4);
}

.element {
  color: var(--fading-night);
  background-color: hsl(210 81% 45%);
  border-color: oklch(0.562 0.165 253.4);
}

Tailwind CSS v4

@theme {
  --color-fading-night: #1675d2;
  --color-fading-night-50: #d6f8ff;
  --color-fading-night-100: #c4ebff;
  --color-fading-night-200: #a5d8ff;
  --color-fading-night-300: #7cbaff;
  --color-fading-night-400: #50a1fd;
  --color-fading-night-500: #1c86ef;
  --color-fading-night-600: #1b72ca;
  --color-fading-night-700: #165ba2;
  --color-fading-night-800: #064379;
  --color-fading-night-900: #052f55;
  --color-fading-night-950: #001b39;
}

SCSS

$fading-night: #1675d2;
$fading-night-rgb: 22, 117, 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);
}