#010511

CSS

:root {
  --dark-rift: #010511;
  --dark-rift-rgb: 1 5 17;
  --dark-rift-oklch: oklch(0.117 0.033 258.4);
}

.element {
  color: var(--dark-rift);
  background-color: hsl(225 89% 4%);
  border-color: oklch(0.117 0.033 258.4);
}

Tailwind CSS v4

@theme {
  --color-dark-rift: #010511;
  --color-dark-rift-50: #f0f5ff;
  --color-dark-rift-100: #e2e8f3;
  --color-dark-rift-200: #ccd5e3;
  --color-dark-rift-300: #aeb8c9;
  --color-dark-rift-400: #939fb2;
  --color-dark-rift-500: #79879c;
  --color-dark-rift-600: #677284;
  --color-dark-rift-700: #525b6a;
  --color-dark-rift-800: #3b434e;
  --color-dark-rift-900: #292e36;
  --color-dark-rift-950: #161b21;
}

SCSS

$dark-rift: #010511;
$dark-rift-rgb: 1, 5, 17;
$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);
}