#030912

CSS

:root {
  --dark-rift: #030912;
  --dark-rift-rgb: 3 9 18;
  --dark-rift-oklch: oklch(0.137 0.024 251.4);
}

.element {
  color: var(--dark-rift);
  background-color: hsl(216 71% 4%);
  border-color: oklch(0.137 0.024 251.4);
}

Tailwind CSS v4

@theme {
  --color-dark-rift: #030912;
  --color-dark-rift-50: #f0f6fc;
  --color-dark-rift-100: #e2e8f0;
  --color-dark-rift-200: #cdd5df;
  --color-dark-rift-300: #afb8c4;
  --color-dark-rift-400: #94a0ad;
  --color-dark-rift-500: #7b8896;
  --color-dark-rift-600: #68737f;
  --color-dark-rift-700: #535c66;
  --color-dark-rift-800: #3c434b;
  --color-dark-rift-900: #292e34;
  --color-dark-rift-950: #171b1f;
}

SCSS

$dark-rift: #030912;
$dark-rift-rgb: 3, 9, 18;
$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);
}