#00040D

CSS

:root {
  --dark-rift: #00040d;
  --dark-rift-rgb: 0 4 13;
  --dark-rift-oklch: oklch(0.105 0.03 250.1);
}

.element {
  color: var(--dark-rift);
  background-color: hsl(222 100% 3%);
  border-color: oklch(0.105 0.03 250.1);
}

Tailwind CSS v4

@theme {
  --color-dark-rift: #00040d;
  --color-dark-rift-50: #eff6fe;
  --color-dark-rift-100: #e1e9f2;
  --color-dark-rift-200: #cbd5e1;
  --color-dark-rift-300: #adb9c7;
  --color-dark-rift-400: #92a0b0;
  --color-dark-rift-500: #78889a;
  --color-dark-rift-600: #657382;
  --color-dark-rift-700: #515c68;
  --color-dark-rift-800: #3a434c;
  --color-dark-rift-900: #282f35;
  --color-dark-rift-950: #161b20;
}

SCSS

$dark-rift: #00040d;
$dark-rift-rgb: 0, 4, 13;
$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);
}