#010510

CSS

:root {
  --dark-rift: #010510;
  --dark-rift-rgb: 1 5 16;
  --dark-rift-oklch: oklch(0.116 0.031 257.1);
}

.element {
  color: var(--dark-rift);
  background-color: hsl(224 88% 3%);
  border-color: oklch(0.116 0.031 257.1);
}

Tailwind CSS v4

@theme {
  --color-dark-rift: #010510;
  --color-dark-rift-50: #f0f6fe;
  --color-dark-rift-100: #e2e8f2;
  --color-dark-rift-200: #cdd5e2;
  --color-dark-rift-300: #aeb8c8;
  --color-dark-rift-400: #939fb1;
  --color-dark-rift-500: #79879b;
  --color-dark-rift-600: #677383;
  --color-dark-rift-700: #525c69;
  --color-dark-rift-800: #3b434d;
  --color-dark-rift-900: #292e36;
  --color-dark-rift-950: #171b21;
}

SCSS

$dark-rift: #010510;
$dark-rift-rgb: 1, 5, 16;
$dark-rift-light: mix(#fff, $dark-rift, 20%);
$dark-rift-dark: mix(#000, $dark-rift, 20%);

.element {
  color: $dark-rift;
  box-shadow: 0 0 0 2px rgba($dark-rift, 0.35);
}