#2D37A6

CSS

:root {
  --depths-of-night: #2d37a6;
  --depths-of-night-rgb: 45 55 166;
  --depths-of-night-oklch: oklch(0.406 0.176 271.8);
}

.element {
  color: var(--depths-of-night);
  background-color: hsl(235 57% 41%);
  border-color: oklch(0.406 0.176 271.8);
}

Tailwind CSS v4

@theme {
  --color-depths-of-night: #2d37a6;
  --color-depths-of-night-50: #e5f3ff;
  --color-depths-of-night-100: #d5e4ff;
  --color-depths-of-night-200: #bccfff;
  --color-depths-of-night-300: #9bb0ff;
  --color-depths-of-night-400: #7b94ff;
  --color-depths-of-night-500: #6077f8;
  --color-depths-of-night-600: #5165d1;
  --color-depths-of-night-700: #4051a8;
  --color-depths-of-night-800: #2b3c7e;
  --color-depths-of-night-900: #1d2959;
  --color-depths-of-night-950: #0e163d;
}

SCSS

$depths-of-night: #2d37a6;
$depths-of-night-rgb: 45, 55, 166;
$depths-of-night-light: mix(#fff, $depths-of-night, 20%);
$depths-of-night-dark: mix(#000, $depths-of-night, 20%);

.element {
  color: $depths-of-night;
  box-shadow: 0 0 0 2px rgba($depths-of-night, 0.35);
}